I think because you enable account verification via email.
So, you need to activate the account via email first, then they can login.
Thats why it said your account has been banned. Because the account isnt being verified yet via Email.
Just disable email verification in flux if you didnt need it.
Btw actually you doesnt need to change access.php , just use default fluxcp latest and also rathena latest from github.
Please use the latest one for both, because any changes by themes/etc or different rathena (older vs latest) version might give you an issue.
There are so many databases changes within this few years.