Hey @matt, thanks for getting back so quickly 
Hm, noticed something even weirder now. I went to my test instance to get logs for you, because masto.donte just has too much stuff scrolling around and it was working fine. The only difference between the two is that my testing was still in 3.2.0 and masto.donte.com.br is in 3.2.1. But I think we can eliminate authorized fetch, because my test instance also has authorized fetch on.
So I’ve bumped the version of my test instance to see what happens, and it still worked, which led me to think there was something else going on the first time around (and no doubt about it, now it shows as being followed back in masto.donte.com.br too)
Do you think it could be some kind of slower federation queue that would cause it? (Not sure if there’s even a federation queue in write.as as in mastodon)
The original blog that was reported as not working is in a custom write.as instance, so I’m guessing it might be actually related to Unable to follow blog [SOLVED], I’ll check with the owner of the instance to get some logs and see if there’s something going on there