This thread tells how to do hard reset of T2. Should return to original firmware that was on the reader. You will have to register your reader again to your old account. It will want to update to latest firmware.
https://www.mobileread.com/forums/sho...d.php?t=206747
How many books do you have loaded onto your reader and external SD card? I have more than 2000 public domain books on SD card. Must turn off display of covers for library or reader will freeze trying to handle that many covers.