With PRS+ you cannot brick the reader! That's a fact. So:
Did you do other "things" with the firmware on the reader?
If yes: yes, you can "toast" it (I did it...).
- Solution: that depends on... (I had to call Sony...)
If no:
- hardware is defective --> call Sony
- software is defective --> factory restore (not just reformating! You should have 3 sample books on the reader after factory reset)
I have had same behaviour of my reader like you (no connection to the reader via PC). First time a factory restore did the job. Second time I bricked the reader with faulty firmware. No change for me to fix it --> Sony did the job.
A.