Can HD Native PCIe/Omni Co-Exist With Another Interface?

[sarcanon]

I have a Windows 10 PC rig that had previously been running Pro Tools 12.7.1 (standard), with an RME HDSPe RayDAT interface.

I've now acquired a second hand HD Native PCIe card and an HD Omni, in addition to a Pro Tools 12.7 HD license and the DigiLink license. All software/licenses are activated and visible in my iLok account.

However, Pro Tools HD will not recognize the Omni. The RME is (and always has been recognized) in the Setup->Hardware dialog as "ASIO Hammerfall DSP". But the Omni does not appear. I've run the DigiTest utility application, and both the PCIe card and the Omni are recognized on the Slot Info tab.

After Googling about, I cannot find any information about whether this configuration is supported or not, i.e., can the HD Native PCIe/HD Omni co-exist with the RayDat interface?

Many thanks in advance for any advice on how I can get going with the Omni.

P.S. I've started a support case with Avid, but I find they are rather slow to respond.