I’ll be keeping this post up to date as I work through the issue. I’m marking this as the ‘solution’ so that it’s included in the top post.
I accidentally broke ~400 city syncs and I need to reprocess tons of data to get everyone’s progress fixed up. I’ll prioritize cities mentioned here, but everything will eventually get sorted out. There is no action required/possible for you to correct this. I’m purposefully skipping accounts that haven’t been logged into in the past month, to speed things up for people who actually use CityStrides. 
If you would like your city prioritized, please share the link to the city (either your custom view or the plain city page, either works).
While I still have about 300 cities left to reprocess, I’ve made it through most of the shared cities in this thread.