I’ve done an ooops and reset the Follow network: you may have to re-follow people manually all over again.
This may be an opportunity to re-assess who you follow?
A reminder that you can follow people via the User Card of the person you wish to follow, accessed by clicking their avatar.
Profuse apologies!!
(It might be possible to restore it but this will be a significant amount of work. Let me know if it’s really critical to you.)