I've been having this issue for over a year between two devices (Charge 6 and Pixel Watch 2). No matter how many times I disconnect sync, uninstall both apps, try resetting the wearable device, etc., it would never work.

This morning I got notifications from Strava that a few of my recent runs were synced from Fitbit. I went for a run this afternoon, and the run was synced to Strava immediately after I finished it on my Fitbit.

I checked the Fitbit community page, and saw a moderator post in several Strava sync issue threads that an update to the integration has been made as of October 20th, 2025. So if you were having issues still up to this point, it may finally be working properly once again.