Jumping into this discussion as I have the same issue...
Mac is on Monterey 12.3.1
FCP is on 10.6.2
Compressor is 4.6.1
I'm not sure which Pro Video Formats version I am on but I have recently updated, so assume it's 2.2.3
Send to Compressor from FCP inevitably leads to a Missing Plugin message.
Sharing from FCP works fine.
I have tested via the same hard drive on a laptop, which worked (although that laptop is freaking out in other ways, with compressor refusing to open, so perhaps the same problem is showing up in a different way?)
The media on this particular library and project is all from a Sony FS700 - other projects on the same drive have Black Magic derived footage (but transcoded to ProRes) and GH5 footage too.
I think it's a drive issue, as opening one of the same projects on a backup hard drive doesn't cause the same issue.
Any thoughts, or just...back up and move on?!
Thanks,
Josh