Resurrecting an instance and Federation

I have an instance (mander.xyz) for which the database was deleted, and I have set up a fresh new instance at the same domain.

Federation appears to still be enabled with lemmy.ml, but I am having general issues fetching and interacting.

For example, if I try to access https://mander.xyz/c/linux@lemmy.ml, the error log shows:

2021-12-11T17:53:52.201426Z ERROR lemmy_websocket::handlers: Error during message handling error sending request for url (https://lemmy.ml/.well-known/webfinger?resource=acct:linux@lemmy.ml): error trying to connect: dns error: failed to lookup address information: Try again

I posted a somewhat related issue on GitHub , and it was pointed out by dessalines that "An activitypub actor id must be unique, and you recreated one with new public and private keys". It is not clear to me whether these ids apply only to specific usernames, or if the actor is a more general concept (community, post, instance as a whole) to the point that federation is irreversibly broken.

Are there steps I can take to fix the federation? Or is starting a new instance using a different domain the only way forward to re-enable federation?

I do want to point out that during certain periods of the day federation suddenly appears to work just fine for a few minutes.

Thank you!