HD Omni + HD Native Help

[DR-HM]

I recently purchased a brand new HD native plus a used HD Omni interface (from Reverb without registration info) and I can't hear any feedback OR select the HD hardware in the playback engine within Pro Tools. I'm currently running Pro Tools Studio Perpetual (2021.10) and I suspect that is the issue. I'm a bit confused on whether I need the "AVID PRO TOOLS DIGILINK I/O LICENSE" or if I should be purchasing Pro Tools Ultimate Perpetual..? I've read that the HD Omni typically comes with the HD download/software however, since mine is used I don't believe I'll have it and just want to make sure I download the right thing to solve this. Any help is appreciated!