No login option in app

For over a month support has been unable to sort this issue out. Twice they've told me to do things
I'd already tried; even though, at the time I didn't think it made sense. It didn't work the first time. or the second.

Musescore was giving me problems on my Tablet to I reinstalled it and found the only option that was presented was to Join; enter my name, check all the boxes, etc.

Why isn't there a "log-on" option for paid-up, Pro members?

In their most recent response, I was told; "Dev says you have to enter all that information, again,, at which point you will see a "log-0n" option.

That is sooo counter-intuitive! Why enter all that information again, before logging on?

Why would anyone intuit go through that process in order to get a password prompt?

Something is very wrong here, it doesn't feel like we are on the same page. How could this issue cause to much confusion, for such a long time?