Failed to Sync Workouts

Workout sync has been failing the last couple of weeks, with the message "Failed to Sync Workouts." I've used it a bunch in the past, but not recently, so I don't know exactly when this started occurring. I did just upgrade from a Karoo 2 to a Karoo 3, and I didn't have this problem before that, but I think that's probably a coincidence?

My workflow is Join Cycling app -> Export to Trainingpeaks based on power -> Sync to Hammerhead. I can see the workout on Trainingpeaks and it's syncing fine to other services, but not to Hammerhead. I tried disconnecting and reconnecting Trainingpeaks. and I also tried manually creating a workout on Trainingpeaks. Neither resulted in a successful sync.

Any idea wha'ts going on here or how to fix it? My current workaround is exporting to a .zwo file and importing manually which is kind of a pain.