Flashforge Invetor II failure

I've been asked to look at a Flashforge Inventor ii. I has zero files on internal storage and displays zero available. I did the factory reset and there was no change. The internal storage is still full.
Aside from that, there are a couple more repeatable failure modes.
1. Firmware updates via PC software, USB and Wifi all fail with 'network/file failure'.
2. Sending files to the printer still fails with 'network/file failure.;
3. Preheat the extruder hits 220C and stops there.
I've reseated all the connectors on the main board. Is there a secret diagnostic boot sequence? Is there a way to get more information from the printer?
Thank you.