If you search the forums you will find this is a known issue for many users with the recent updates. They are reportedly working on a fix, but no timeline has been communicated (it has been over three months so I would not hold my breath). I suspect since they have already left the market and are not producing any new devices they may never fix it. In the meanwhile you always have the option of syncing via computer. If you go to this post and ask the moderator to roll back your firmware version it should fix it, although you will lose the Fitness Points and Fit age features:https://en.discussions.tomtom.com/spark-and-spark-3-runner-2-and-runner-3-473/unable-to-pair-sync-after-update-to-firmware-v1-7-53-runner-and-spark-watch-series-1030088
I hope this helped answer your question. If so, please mark it as a solution so others can look for it if they have the same question.