Hello,
the script you have recorded starts with filling a a logon screen. Of course, you also need one when playing back. So you need to specify the connection also, like
guistart conn=/H/appserver.acme.com/S/3200 -f testscript
Another option is to specify the logon data in parameters like
guistart conn=/H/appserver.acme.com/S/3200&user=guest&pass=secret&tran=mytransaction
It is the same as saving a connection in SAP Logon and providing the logon data in the "logon" tab of the new connection dialog.
A safer approach regarding passwords would be to use Secure Network Connection including authentication.
Best regards
Rolf-Martin