Zip stopped working after successful version update.

[ITRick]

I recently obtained an iPhone XS and installed the App on it to sync my Zip FitBit to.  On successful setup and sync of Zip on the iPhone using the App I was prompted to perform an update to the Zip.  I replaced the battery in the Zip and reconnected to my iPhone.  I performed the update to the Zip successfully as the progress bar indicated it was complete. I tried to sync the data and it no longer would transfer any data after the update. I tried for several minutes to connect and sync.  The device is recognized but won't sync.   The next morning I removed the battery and rebooted my phone and even installed the Windows App and tried to use the dongle.  It sees the device prompts for the 4 digit code but fails to setup giving an error message. "com.fitbit.http error 400". Please advise of the fix for this issue so that I can restore functionality to my fitbit Zip as quickly as possible.

[Rich_Laue]

Help us, for clarification. 

You say the zip won't sync, then you mention that you can't set it up. 

Which is it? Is the Zip connected to your Fitbit account? If so you do not need to set it up.