Partially answering my own question here, but I sort of have this working now.
I added to the configuration:
"target.device_has_remove": ["SLEEP"]
This allows the device to enumerate and also work now.
But, it seems like this should not necessarily be a requirement to get the USB device working with MBED OS.
While it’s a different processor and USB port, I got the idea from this chain: https://github.com/ARMmbed/mbed-os/issues/13641.
Any thoughts on why this is required? Also, has anyone had success with this port?