TrekStor Customer Support
I contacted TrekStor via their website on 22 Feb. and got their email response today, 27 Feb.
I had sent them this: "After the TrekStor eReader Suite failed to install, my Pyrus Mini no longer shows up under My Computer. It now simply shows as Removable Disk (J: ) and Removable Disk (K: ).
I can no longer access my Mini with my pc. Clicking on Removable Disk (J: ) now only brings up the error message "Please enter a disk into drive (J: )"
I could still read the epub books on my Mini, until after I tried both Format Device and Factory Reset."
Their response was, "this problem could be caused by a defective cable. If you have a replacment cable, please try to with the pyrus mini on another usb-port or another computer." Uh, right.
Luckily I was able to use the reader's built-in explorer to delete a new file (something like machineinfo.ini in the Digital Editions folder) that had appeared after the failed suite installation and that fixed everything.
Even the cable magically fixed itself, hehe