Recently found out that all my posts on Mastodon were going into a black hole. No errors, but not being shared with anyone either (even on my own instance).
But the problem also explains why it's seemed so quiet on Mastodon lately... the instance I am on also wasn't showing me any new posts.
No error messages.
Eventually I found the announcement that they're shutting down in < 30 days and I managed to get migrated off there. So far about 1% of my followers have been migrated over.