Garmin Connect fails to synchronise my sleep data from my FR945 as per today.

Thank you for your insight and support. Today the situation is equal to yesterday. All data are synchronized to Garmin Connect (GC) , except sleep data. The GC app shows the sleep data until two days ago, so is not lost. The sleep has been recorded and has been measured as usual on my FR945. It is just the sync of the sleep data with the app that doesn't work. 

Update 

I checked the sleep data in the GC app for the last week and I noticed an issue with the registration of my breathing (see screenprints attached to my original post). Every sleep recording consist of three separate parts: sleep phase, O2 saturation (is optional and I don't register that to save battery) and breathing pattern, see 1st and 2nd screenprint. The last two nights it appears no breathing has been recorded during the night (see 1st and 2nd screenprint). But if you take a look at the 3rd screenprint it shows the registration of breathing during night and day, so it was registered. But as part of the sleep data it looks like the night registration of breathing didn't happen. As this is the case on these two nights I suspect this is related to the issue I posted (sleep data are on the watch but are not being synchronized). 

If the data is available on your watch and does not sync to Garmin Connect, then try removing the watch from the app, signing out of the app, signing back in, rebooting the watch and adding the it back to the app.

More detailed instructions are available here: Data is Missing from My Garmin Connect Account After Syncing | Garmin Support. Some other tips also here Troubleshooting guide for (some) data missing after syncing

Good day, thanx for your advice. I already did exactly that yesterday, with no succes. 

My FR945 was updated last week (March 6th). I come to suspect it is issue is correlated with this update. Yet another strange thing happened this am. I was choosing cycling as an activity and when I pushed the button on the watch this blue triangle appeared (like when turning it on). It took seconds before I could operate the watch and choose for a cycling training. This is somewhat similar as to what happened yesterday. I was underway and wanted to check a training option on my watch. I pushed the button and this blue triangle appeared. Then the watch (not like today) rebooted spontaneously. 

In that case, I recommend resetting the watch to factory defaults. Better told, first of all, check for updates with Garmin Express, and install the latest firmware, if the watch is not up-to-date.

And if even these measures do not help, contact the Support and ask a replacement watch.