Do you have any 12 volt load to hook directly to the converter and remove the other 12 volt loads?
Appears you have a 70 amp 24 volt to 12 volt converter. I had one of those bad out of the box. Got a replacement and two and a half years later running fine.
If the load works, may be a 12 volt wiring problem. If the 12 volt load doesn’t work, points to the converter or the 24 volts into it.
I use my 70 amp inverter for a 50 amp load for a few seconds at a time with no issues.