This started last night. My Fenix 5X has reliably transferred an activity to wifi daily or every other day as activities change. First off was within a few seconds it showed the error that it could not connect to wifi. I was sitting next to my router and on my workstation. I had internet service. So wired the unit and did a sync, but also verified my wifi was listed and for good measure entered it again. Disconnected my Fenix and attempted a wifi sync and successfully showed the green screen.
Today did a cycling activity and came home and attempted a sync and again. Error screen connecting. Tried a second time and began to transfer. Looked like it was going to work but again, threw an error. I switched over to Bluetooth and Android which was connected to my wifi and successfully uploaded the activity.
Again.... This was a back end issue a year ago I believe as after a month or two of those wifi screen errors it all of a sudden vanished.
It also may have something do do with the activity duplications recently. I have not had a duplicate in 2 days now, but am having the sync error, so my gut is telling me Garmin is working on something and it's causing these glitches across all devices.