Thank you for your reply.
I have tried support but they aren’t replying. Sylenth1 does work but just not for me. I’m at an end to what other setting to change. I’ve only just realised, the P6 screen actually shows the parameters intended for a fraction of a second, then discards them all for just the Master Filter. I may have to send mine back or there’s a cubase setting messed up, or file somewhere conflicting.