Multiple microphone channels with iOS and RME Fireface UCX II?

Is anyone managing to get multiple microphone channels with the iOS version? I was achieving 4 separate channels with my old Akai EIE Pro running on an old PC, but having shelled out a pretty eye-watering sum on an RME, which has multiple outputs, I’m getting five output channels, but here’s the thing: they’re only fed by the first two microphones. When I try to activate further microphones in separate channels, the output channels 3 to 5 remain greyed out. The mics, all mics, work fine within channels 1 and 2.

At this point, I don’t know whether this is a Pianoteq or an RME issue - Pianoteq sees the five activated output channels that I have connected to the RME, and a mix of the microphones feeding outputs 1 and 2 comes out of them. However, Pianoteq does not see the RME as an interface in options, only making iOS Audio available. The RME is running in class compliant mode.

So, is anyone else succeeding in getting output from more channels than just 1 and 2 in the iOS version, with any sound card?

Has anyone successfully got Pianoteq to recognise an RME Fireface UCX II in the device dialog box, and if so, can you get more than two channels working?

My iPad is an Air 4 (A14 Bionic chip, seen as an M1 by Pianoteq!) and works very well, aside from this channel porting issue. I’m trying to get five mics into five separate channels - the two channels in my Yam N3, two Mackie HR824 studio monitors and a further Motion Sound speaker.

If anyone has managed to get a similar five (or four) -channel arrangement working with the iOS app could you tell me which usb interface you are using?