Your 8ohm channel is fried why happened was you ran 2 12s in an 8ohm load and turned it down to 2ohms the speakers was pulling all the power and that made it over heat and when it over heated it fried you're amp. It ain't no good you can't fix that
When an amplifier causes trouble or otherwise stops working, it is necessary to eliminate external possibilities such as a short circuited output.
If nothing external is causing the problem, unless you have a good friend who is an electronics engineer, it will be a repair shop task...
Check your fuses. Check to see if any of the wires are loose. Could be a blown fuse or loose wire.
Possibly the following link might be of interest:
https://www.youtube.com/watch?v=xMbsieEj0UM
