PM just doesn't seem to think anything is on any card in these readers. On a couple of attempts it will import a single image from one or two of the cards in the unit before claiming that all the ingests are complete with a green bar of success. Again, I can read and copy from Finder and Lightroom. PM has worked for me the last 5 years using a variety of other readers. Does PM require that the drive be writable in order to somehow communicate during the ingest process? If so, these are read only drives I believe.
PM does want to write a .pmingest.dat file to the drive so that Incremental Ingest can work. Are you using Incremental Ingest and have you ingested those images before?
There is a logging facility built into PM5. You need to create a plain text file named PMDebug.txt and it has to be in PM's Preferences folder.
PM's Preferences folder will be in the following location:
~/Library/Preferences/com.camerabits.PhotoMechanic/
Unfortunately Apple decided a few OS versions ago to hide the Library folder within your home folder. You can still get there though by using the "Go to Folder..." command on the Go menu in the finder. Enter the path above in the dialog that appears.
Create your PMDebug.txt file there and make it have the following contents:
INGEST_LOGGING ON
Save the file and relaunch PM5 and try to do your Ingest. You can then use the "Reveal Support Data..." command on the Help menu and post the zipped log file here.
Thanks,
-Kirk