Well adminencrypt.php should be inside the upgrade folder, upload it to your server and run it to solve your problem.
I see, the way login form is designed is the cause of your problem. As you may have seen from elements or simple theme, the login form is located at the sidebar. The center space is left blank for some reason, just look at the screenshots below and you will understand what I mean.
Elements:
Simple:
It seems that your site does not have sidebar, and therefore the login will not display. I will see if there is a way to move login form to the center instead of its original location at sidebar, this is the one and only way to fix your issue.
Edit: I reuploaded the Mys v1.2.3 files after fixing levelup.php glitch, since I believe this one is not a minor issue we can let pass till Mys v1.2.4. I am sorry for the trouble, guys and gals, how I hate typos...