Interfacing a CMT 54 Test Set Rohde&Schwartz through GPIB USB HS

Hi community, I need help, please.

I own an old Test Set R&S badged CMT 54.

I'd like to interface this gear with NI GPIB USB HS but... nothing to do.

I pinpoint that

1. GPIB HS interfaces other instruments successfully

2. NIMAX recognizes the presence of an instrument at the right GPIB address but is unable to send any commands.

Does someone have any skill/experience to share?

Thank you