Hi! I understand your Reeder app on your Mac running OS X 10.15.7 is stuck syncing with the update arrow endlessly turning and no new updates since yesterday. Let’s work through this together.

First, just to clarify:
- Are you using iCloud syncing or another sync service within Reeder?
- Have you tried quitting and restarting the Reeder app?
- Did you notice any internet connectivity issues around the time it stopped syncing?

Once I have this info, here are some initial steps you can try that often resolve syncing stalls:

1. Check your internet connection — Make sure your Mac is connected and stable.
2. Restart Reeder — Quit the app completely (Cmd + Q) and relaunch it.
3. Force sync — Some versions of Reeder have a manual sync option in the app’s menu. Try triggering that.
4. Sign out and back-in on iCloud or the sync service — If you use iCloud for syncing subscriptions and timeline, signing out and back in can reset the sync connection.
5. Delete and re-add problematic feeds — Sometimes a corrupt feed stalls syncing; removing and adding it back can help.

If these don’t resolve the issue, the problem might be deeper like a corrupted sync database or ongoing issues reported with Reeder's iCloud integration, which have been known in past updates1 2.

Let me know what you’ve tried and your answers to the above questions, so I can guide you with more targeted steps from there!