The solution depends what did the administrator exactly.

First try pressing CTRL+SHIFT+F1 function key and enter the admin credentials.

In case it still doestn't work it is possible to recover the account with DB tweak, but the steps depending on the previous modifications made:

The database can be modified with the help of SQL Management Studio.
The authentication settings stored in the FUNC_CONFIG table.

Edit the table qnet6.FUNC_CONFIG, and search for the line, where the value of FC_PARAM is 36. delete this line.
It will not affect immediately, as the application using hibernate cache and not refreshing the modifications out of the application, so you'll have to restart the service.
Then you should be able to login with admin/admin

If the admin user still doesn't work then it is possible that the password had been changed or this user had been deleted.
In this case edit the qnet6.USERS table. 
Search for the line where USR_LOGIN is "admin". Check USR_STA.
If its value is "A", then the account is active. If "D", then deleted.
Change to "A" and restart q-net server service.

In case the password of admin had been modified, edit the USR_PWD field of "admin" user, enter the below string:


After that restart service, and try login with admin/admin.