Have you checked out these syncing troubleshoots @Lewi? Also, make sure that there isn't another bluetooth device that may be creating interference during the process. Setting up your tracker as a new device may also help you to bring it back to sync as usual. If you already have gone through those steps, please be sure to reach out to our Support Team. I know that they're always happy to listen to your experience and provide different options for you, if needed!
Hope this helps. Let me know the outcome.
