What glue to fix flex bracelet that came apart

Yours is not an uncommon problem. Try this link for a bit of help.
https://www.livescience.com/47264-fitbit-flex-hold-charge.html

Fitbit Returns Warranty


https://www.fitbit.com/legal/returns-and-warranty


Appears from web site that warranty is for 45 days with approval.

FitBit Flex General Setup and Charging Tutorial
Please follow this steps
and fix it
Blessing
[email protected]
cell+whatsApp: +50588611441

Superglue would work I would think or Gorilla glue.

Contact.fitbit.com You will also find thos info in the warranty, this can be found at the bottom of any page on fitbit

How to fix broken Fitbit - sync Fitbit with phone app - PC ...

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May 15, 2015 - Fitbit Flex, Fitbit One, Fitbit Zip, Fitbit Force or Ultra not syncing with the Fitbit app ... To get the Fitbit app sync working again restart the Fitbit tracker. ... charger, has a battery charge but is not lighting up, or isn't tracking your steps. .... I've already done all the obvious stuff: turning off my phone, turning off and ...

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May 5, 2013 - My wife and I are both in good shape, we both wanted the Flex just to ... app, wait for the device to finish connecting and syncing to your phone, ... to sleep mode, I have to do all of this? and then again to wake it up? .... Also, doesn't the manual say "not" to wear it in the shower? ..... I appreciate any response.

Sounds like you need to re-sinc the fitbit to the computer via dongle, or via smartphone.

Sears will definitely come fix that under the warranty. I was in that line of work for years, and we would come fix any problem on a machine under warranty.