Heated print bed causing shut down

Hi everyone.

I am using a Tenlog TL D3Pro that I purchased a few years ago. Yesterday it cut off as I was warming up for a print. After some trial and error I determined that it was a problem with the heated bed. I can turn on the machine and it will stay on until I try to heat up the bed and then it cuts off. It will come back on in a few seconds and run fine until I try to heat the bed again.

I checked where the wires are connected to the bed and followed them in to where they connect to the board inside the box. There is no sign of damaged or burned wires.

My question is - How can I tell what the problem is. I am far from an electronics expert. I have learned a little thru trial and error by working on the printer I had before this one - a Tronxy XY. But, with no visual evidence of where the problem originates, I don't know whether I need new wiring or something else. I would rather not have to just order parts and try them one at a time. Especially since it takes forever to get parts.
I will attach some pics of the wiring.

Thanks for any suggestions.

Donna