25.00 - no sync to phone

Still could be a DST problem but it only shows up 25.00 though?  And maybe only with Android GCM, the folks I've seen post their phone specs are all Android albeit on different versions. 

Again, this is definitely not GCM / phone issue because when Bluetooth doesn't work on the watch, it doesn't work with _any_ devices. Feel free to try to connect to e.g. Bluetooth headphones - you'll see that doesn't work either.

Another data point - 

When the sync is broken, connect the watch to a pc of some kind so it goes into usb storage mode and delete the files out of the .fit folder.  When you unplug the watch you can sync with the phone again without having to reboot the watch or phone. 

Observations are as such - 

Not syncing this morning. 
Watch is connected (green dot in GCM). 
Click Sync in GCM on phone. 
Sync progress bar starts, goes to about 1:00 and stops for 60 seconds. Then progress bar goes away. 
Sync button still has a green dot on it. 
Click Sync again and the sync arrows on the sync button spins for 60 seconds then nothing. 
Attach watch to Mac.  NOTE:  When you attach the watch to a power source BT, HR sensor etc, on the watch turns off as validated by it not showing as connected in the phone and not visible to BT and LED's going dark.  
Open drive, go to activities, 5 .fit files stuck in it.  Delete those.
Unplug watch, wait for clock face to reappear. 
Hit Sync button in GCM. 
Sync starts, progress bar goes all the way around and my overnight stats (sleep, RHR etc) show up in GCM. 

I can repeat these symptoms and observations I have no doubt tomorrow. 

Next thing to try when it's broken is disabling BT on the watch manually by turning off Phone in the settings which I assume (hope) that results in the same BT off/on that plugging it into power does. [Update:  <-- that worked]

That's not my current experience. :(.  I just confirmed that my sync to the phone is stuck.  I started an activity, saved it on the watch.  Clicked sync on phone.  No data, no progress bar, just a spinny sync. button.   

Turned on my aftershockz, opened Spotify, paired right up and plays music. 

Hit sync on the phone.  Nothing, spinny cursor of death. 

Got to Watch - Settings - Phone - Shows connected and now it gets interesting.   

I press upper right to disconnect it and I get a FAILED message at the top of the screen on the watch, that sat there for a few sends then the status went to Off. 

Headphones are _still_ playing so it didn't turn off BT, it only disco'd the phone. 

I press it again to connect the phone back and it syncs the activity to the phone. 

Since my data points are scattered around I'm collecting them here in case it's useful - 

Fenix 6X Pro - 25.10
Pixel 7 Pro - Android 13, GCM (current)

One thing I want to call out is my phone OS and hardware have not changed in close to a year.  Only GCM on the phone and the FW on the watch have been updated in this time frame. 

Sync issues started this year (2023) and have gotten progressively worse it feels like.  Started with 25.00 on the watch.  Continues with 25.10.  Others report it continues out to 25.77 beta. 

Other oddities noticed.  .fit files were found stuck in Activities folder going back to November.  These were deleted manually.  .fit files continue to not be removed after successful import.  I don't know if this is an issue or by design.  I thought deleting these was a fix but it actually appears to just be connecting the watch to USB and disconnecting it that was the actual fix, these stuck files appear to be a potential red herring. 

The symptoms of a stuck sync for me are - 

No data shows up (d'uh)
Hitting sync in GCM may or may not give you a progress bar that crawls around to 3:00 on the dial and then stops for 60 seconds then just stops. 
Hitting sync in GCM after that no progress bar, just the spinning sync button. No data. 
Watch icon shows green connected dot. 
Notifications from the phone events (text/call) aren't showing up.  

Other data points: 

BT headphones work fine for me when the sync is stuck including switching between different pairs. 

The following things each individually fix it temporarily for me and my watch+phone today in testing - 

Reboot watch (works every time, tested multiple times in the past, once today)
Go to Settings - Phone - Turn off - Turn on (works every time, tried 4 times)
Plug watch into computer, unplug watch (works every time, tried 4 times)
Go to Phone - BT - Turn off - turn on (works every time today, tried 3 times)
Force kill GCM on the phone, open it back up, let GCM connect (works every time, tried 5 or 6 times) 
Wrap the watch in foil and take to far side of house so they lose connection with each other. (worked both times I tried it)

Easiest fix for me is to force close GCM and open it back up.  YMMV. 

So the root cause of all the fixes today for me anyway seems to be breaking the connection between the watch and GCM when it's stuck and then you get either a short window of successful sync events or just two-three syncs and then its stuck again. 

Currently the 'works every time' fixes results in this observed behaviour - 

It works for 2 to 3 manual sync events right now if I do any one of the above, and immediately hit Sync in GCM i get a successful sync, progress bar goes all the way around. Waiting for each one to finish and clicking it again, on the third sometimes fourth subsequent pressing of the sync button the sync button just spins, no progress bar. 

Hope that info helps folks. 

Chiming in here. My fenix 6 sapphire started intermittently disconnecting about a week ago if it was more than a few feet away from my phone. Then a couple days ago it finally disconnected permanently. Garmin Connect app could see the watch, and it is visible in the bluetooth devices available to pair (not as a saved device), but when attempting to pair it would throw an error about an incorrect PIN or passkey.

I tried on multiple android phones, one fully updated Pixel 5a with the latest security patches and everything, and and older Pixel 2 stuck on Android 11 and last security patch from 2020. Same error on both phones.

I could get the app to ask for a PIN by going to Apps > System Apps > Bluetooth Legacy and removing the cache. The PIN would appear when pairing but still fail with the same message even when guaranteeing the PIN was entered correctly.

After over an hour on the phone with Garmin support yesterday the rep had me try something interesting. I already confirmed that the bluetooth on the phone works with other devices, and the watch can connect to other devices via bluetooth. But shockingly, if I connect the watch to a bluetooth speaker, THEN try pairing it to my phone IT WORKS! This is where it gets strange: turning on/off the bluetooth speaker will automatically connect/disconnect my watch to my phone.

Reading this thread plus my own experience has me believing this is either the firmware or an issue with the Garmin Connect app. I've already fully reset my watch in hopes that works so now I might try older firmware or the beta to see if the issue persists. If not, I think we know where the issue is.

Very weird about the speaker in general that they'd even bring that up.   Does the pairing on the watch drop when you turn the speaker on and go on when you turn it off?  That's not unusual if that's the case in my experience with BT audio devices.    For example any time I get into the car with my headphones on and working as soon as I turn the car on the radio grabs the BT connection from the headphones.   If I turn off the headphones and turn them back they grab the phone connection back from the car radio. 

Just realized that based on my testing today, that probably explains my syncing seems to fix for a few days at a stretch at time.  I run phoneless about 1/3rd the time. Ergo GCM loses connection with the watch which fixes it for one sync.  Or I leave the phone on one side of the house and go to the other long enough for them to lose connection and voila it works for a sync or two. 

FWIW someone else has already tried the beta FW and it didn't fix it.   The only fix I've seen reported here is going back to 24.10.