I know that you mentioned that you inspected the diaphragms and did not find any issues. I would replace the diaphragms. If your water source is good, your current is good, you are able to turn the solenoids and get the valves to open, you should replace the guts of the valve. solenoids and diaphragms. You may get away with just the diaphragms. There may be other opinions.
Good Luck.
Dan