Hey, so I have the role of Beta tester on my account, says so when I click account from the launcher. I paid for something, not sure what it was - it was awhile ago, but I'm not able to join either the beta or public server. What do I have to do to join?

You gotta install the 1.16.5 version of the Dalek mod (Update 67) found on curseforge. I would also recommend you install JEI With it

The Beta server has been down for a while but is supposedly meant to return soon.