Trouble with Intensity Pro 4K RCA Audio Input and Windows

Windows 10.
I have a BM Intensity Pro 4K PCI card installed. I have an old school cassette deck line out connected to the line in on the BM Intensity card.
I have speakers connected to the BM Intensity Audio Output.
I also have a Behringer UM2 USB Audio Device.
I'm also using Voicemeeter.
I'm trying to record the cassette tape audio in Reaper.
I've connected headphones to the Cassette Deck and can hear audio playing OK.
I've set the Blackmagic Desktop Video software (version 12.8.1) to set the RCA jacks for Audio Input, and tried both Using HiFI audio Levels and not (with levels both maxed high and normal).
Windows sounds work fine over speakers (through BM Intensity Pro) and also over headphones (through the Behringer UM2).
I've just added the Cassette Deck into the mix but no matter what options I've tried, I don't get any audio or see meters working anywhere in VoiceMeeter, Reaper, or Windows.
One thing I 've noticed in Windows Sound settings - on the Recording Tab, the Line In for BM Intensity Pro 4K Audio says "Currently unavailable"

I'm guessing the "Currently Unavailable" for the BM Intensity card is probably the problem, but don't know how to fix that.

Any ideas?
Thanks.

My knowledge may be out of date but I know some older BM cards need a video signal as well as audio to record anything at all.

I connected a BM Pocket 4K to the BM Intensity PCI card via HDMI, but had the PCI card set to take audio from RCA. Still nothing.

I also uninstalled VoiceMeeter and the Behringer USB Audio Device to simply things in hopes of making some progress.

I haven't been using the on-motherboard audio for a while and just disabled that.

The Line-In is still showing "Currently Unavailable"

After further review, I don't think this is going to be possible. I'm trying to work with just audio, no video.
The Intensity capture card seems to not like just any video along with the audio. Well, not digital HDMI type video with Line-in/analog audio.

I'll just use my Behringer UM2 to capture just audio.