For the past several hours I have not been receiving any notifications about posts I have followed. The timestamp for the last followed post notification I received was 2021-07-06 16:23:20Z, and in the 9 hours since then I have seen several comments and answers on posts I followed for which I did not receive notifications. I appear to be receiving other notifications as usual (specifically, I have received notifications for comments on my posts and comments replying to my comments).
Update: This seems to be fixed now. I have been receiving followed post notifications as of 2021-07-07 09:33:56Z, and others also report receiving them recently in the comments below.