I ran into a similar issue and I almost freaked out reading all of these attempts.
But the solution in my case was way easier than I thought. I figured why not try the easy fixes first and then try those hard stuff you guys mentioned.
I just opened their official website again and created an account (signed up) and I clicked again on the assistant and it immediately worked.
Before I did that, it’d show me an error message saying something like “cannot access to file” and other annoying stuff. I hope you find this helpful.
Thanks to everyone here and mostly for Bandlab for making this free for us.