Admin 403 server error

Every once in a while I get a 403 error and it says I'm unable to login. And then magically it clears up. I've had this ever since I signed up for Migadu and I've asked multiple times what the cause is to no answer from support. I use NextDNS but that should cause a 403?

I'm at a loss. I can't manage admin settings when I can't login. I paid $19 a year to move away from proton but at this point, I might keep Proton because I cannot trust this.

Any thoughts or ideas are welcome.