Not sure where to report this - I put a note up on Reddit and I'm not the only one having this issue. If you use the Peloton App (I was traveling and using at a Hotel Gym) any classes will usually sync with Strava - for some reason any of the Walk/Run classes will no longer sync to Strava. You can take a cycling class, a yoga class, a stretch class, anything else - they all sync fine, but the Run/Walk classes no longer sync.
Have had this exact issue for about 2-3 months. I am glad it is not just me!! Same thing, no run classes will upload but everything else will. Feedback initially has been "too many data points" but no resolution. Hopefully a fix soon!
Thanks for reporting this. We are aware of this issue, and are working with Peloton to hopefully resolve this issue going forward. The workaround in the meantime would be to enter the missed activity manually on Strava.
Apologies and please let me know if you have any questions.