Hi
I have similar - my problem started last Friday as it looked like my Charge 3 was not syncing with my Huawei P20 Lite, having been working reasonably well for the previous 6 months. I had one previous issue with syncing, about 3 months ago and went through the unpair and re-pair which took a long time to complete but basically worked just required patience. So I decided to follow same proocedure this time, after doing exercise on both Friday, Saturday and Sunday but not seeing any of this synced back to my phone and clearly syncing was failing.
So I have wasted best part of a whole day wrestling with this problem as each time I got to the point of entering the 4 digits the phone would go to Connecting, then report things taking longer than usual and thereafter it just kept "connecting" but even after 10 mins there was absolutely no sign of progress and would end with tracker displaying a X in a circle and the app suggesting retrying or me just giving up and trying the next trick to try and get it to work. I tried all the usual tricks (turning BT off/on, restarting the phone, removing all previous BT paired devices, updating Fitbit app) with no sign of successful pairing and after about 10 attempts I decided to try using other devices, specifically, my Lenovo Tab 7 and my wife's Samsung Tab A but despite several tries with each they all behaved the same way and I was getting exceedingly frustrated. NOTE: all the phones/tablets tried had system software recently updated.
In desperation, fearing my Charge 3 must be at fault, I went back to the community and found several other posts with similar problems reported against the charge 2 and the charge 3 but tripped over a post which gave the following link (sadly I can't find the original post to give credit)
https://www.youtube.com/watch?v=YRWh3d3wrYc
The basic tenet of the approach in this YouTube video was that some Android update had possibly changed the mapping between variables being passed or the types of variables being passed with the tracker and that you needed to use a device with an older version of Android to get the sync to work. Then use the latest Fitbit app, on the old phone, to sync/update the tracker. Once the tracker was updated then re-pairing to your main device should work. After searching round for some older phones I tried this and finally using a Samsung J3, which had been lying in a drawer for 18 months, the approach actually worked and now my Huawei P20 Lite synchs once again with the Charge 3 tracker, better than before :-).
I can not comment on whether the basic tenet is correct or not or whether just random luck on getting something to pair and then sync enabled the main phone to work but did want to pass the link along in case it helps anybody else.
Cheers
