Open File Options in the File Menu. There are settings there that control what happens with account names and passwords when the file opens. If this is not a password protected file, it should be set to enter "admin" as the account name and the password box should be left empty.
Did some more research, simple solution... the fact that I never set up for admin login at all, it threw me.
Replace the default username (probably first & last name) with "admin" and leave password blank.
If file options are set to enter admin with no password--the default settings for a new file, you should be able to keep a user name other than "admin".