Hello,
It seems that you should connect with SQL Authentication.
If you have forgotten this PW you can reset it with SQL Server Management like this:
You need to write down your new PW as you will not see as you type.
Start and log in SQL Management studio as sa,
On Object Explorer select Security,> Loggins ,> sa,
here you can set a new PW for the server. Write it down and enter it.
Default database is Master.
Use SQL authentication with RMS Administrator to connect and once connected test the connection. Once tested OK RMS Manager and POS should be working.