Hi beyond9thousand,
I am sorry that it does not work for mastodon.social and other instances.
The problem you mentioned is actually already known and it was found out that this was due to a compatibility issue in a new - yet unreleased - version of Mastodon (Mastodon v4). We are having a look into how that can be fixed and made compatible again in a new update of this extension.
The issue tracked in https://github.com/rugk/mastodon-simplified-federation/issues/77. Feel free to follow there follow there to get status updates.

If you have further issues or questions, feel free to ask or suggest a feature by opening an issue on https://github.com/rugk/mastodon-simplified-federation/issues. Thanks.

I hope this explanation helped and continue to have fun using the extension.

Best regards,
rugk