Can't follow someone on a server still marked "unreachable"
If a server is marked as unreachable (for more than a certain time) in the instances
table, no new activities are sent. This includes Follow
activities. From the user's perspective it looks like this: you click Follow on an account of that server, the button changes to "Request sent!" and stays like that. No request is actually sent. No error is reported.
For various reasons servers are sometimes listed as unreachable even though they aren't. E.g. when they're back from the dead. Once a new message comes in from that server, the status resets itself. But if no-one is following a user of that server, e.g. if one or both sides are single-user servers, no new message will come. So that server remains cut off forever.
In the past I have solved this by editing the table in the database, but it would be nice if somehow the unreachable status could reset itself.
Tested on current stable 2.2.1.