Unable to login to 5.0.4 server after upgrade

I upgraded OSX server to version 5.0.4 on a mini running 10.10 using the standard app store method. After the upgrade Server starts and displays the usual "Choose a Mac" screen. I select the mini and am prompted for an administrator login. However, my system admin credentials no longer work. I'm presented with a dialog box stating: "This user is not permitted to administer this server. Make this user an administrator on the server and try again.". The default admin credentials are filled in from keychain, and I only had one administrative account set. Restarting the server doesn't yield a different result. The server admin is the same as the OS X admin and I'm successful using it to administer OS X.

Without an other admin login, there's not much I can do to bring up the server dialog.