I am not sure if the problem is from Indie Hosters’ side, but here is my issue with Mastodon:
I have a personal account on mastodon.indie.host, and an account for my radio show on framapiaf.org.
Both accounts follow each other. The Framapiaf account has posted 18 statuses but the IH account only sees 3, stopping at two months ago. The IH account has posted 132 statuses, but the Framapiaf account only sees 108 (although the latest ones federate instantly).
It seems that IH -> Framapiaf works fairly well, but Framapiaf -> IH is struggling.
Our friends from Framasoft said that it might be a problem with IPv4 vs IPv6.
Any idea? Can I help troubleshoot somehow?