Hope we don't lose the data that hasn't synched from Fitbit to MFP - it's rendering the MFP app pretty useless for me at the moment. I'll try the disconnect/reconnect solution tomorrow but relieved to see it's not just me - MFP has been really clunky since the last update.

MFP seems to have always used a cached incoming system.

Any info coming in hits a cache, MFP tells the sending party it's done and received the data.

The problem is it hasn't gotten out of cache to your account actually - so not really received yet.

But as far as the sending party is concerned - they got acknowledgement it was received - so until there is a change to the data - they don't need to waste their resources and send again.

Sometimes the issue sounds like the cache is really backed up, and just slow.
Sometimes it sounds like the cache has been corrupted and data just lost, so it's never applied.

Throw in the fact the apps are running off different servers that must talk to your account data, and MFP again seems to use a cached response system, the app can think it send the data, but it never makes it to your account.
But it then receives new data from your account to display on the app, but that data isn't actually updated with latest.
So you'll have some parts of the app display stats it received from the device or you entered manually, but totals that must come from the account are wrong.

It's a crazy hodgepodge system of improvements. I'm betting at this point the lines of code are one huge mess to look at and too much to correct, so just keep adding to them and hope you cover all the bases.

Mine just started working again an hour ago. Will see what mood it's in tomorrow. ..

I have also had this issue. Can fit bit do something? It is pretty annoying. The sync between fit bit and MFP worked for months and stopped working in November.