I just started working with my new TOP2004 and I was able to read about 5 chips, then I started having problems. Every chip I try says error on pin 21. I can't see anything wrong with the chip, and it does this even on chips that worked a few minutes ago. Any help would be appreciated.
It seems your programmer ZIF socket has contacting problem on that pin.
Check that pin on ZIF socket. The ZIF socket is removeable from programmer. You can carefully remove the ZIF from the programmer and put it back after clearn the ZIF.
OR you can just turn off the pin detection from the Setting menu.
I had a same problem with Top2048. I fixed it by switching from one chip vendor to another. By the way, in my IC failed pin(s) were not suppose to be connected. Seems like guys are having problems with chip configuration files.