I had the same problem.
The tester has been hanging in the shelf for a while, and I have ordered another one in order to have a basis for comparison.
Your message make me look again at it. No obvious part was looking bad, so after failing to copy the good working Amega328 (which is protected), and veryfying that I had
about 5V on the VCC pin, I swap the chips and it worked.
So, at least in my case, the problem came from the ATMEGA328P chip that was corrupted.
I have a TL866a programmer, but up to now, I have no ben able to reprogram a new Atmega328P with the proper firmware to make it work again.
If some one can tell me how to do it, I will appreciate.