Troubleshooting electrical problem

Not sure either extent of works and doesn't, but check the element in your hot water tank. If it's failed and shorting out then the gfi at the house will trip. I had that and it was difficult to track down but easy to fix once I knew.

You can also try systematically unhooking neutral wires off the main bus for each circuit until you isolate the problem. That is assuming you are comfkrtable with that level of electrical work. Be safe!