I saw a message today that my 5x was updated to 6.0. For lunch did a quick run and the 5x would not sync with the phone and upload. I tried removing the 5x from my bluetooth list and from the garmin app, but now I can't get my 5x to pair with my phone. I've tried re-booting my 5x and my phone several times and having no success.
problem solved. not sure what caused the initial sync problems but the (re-) pairing problems were due to my 5x being paired to a second ios device I owned. Once i un-paired there, i was able to again pair and sync with my 6+ without issues.