do you really have an inverter or are you talking about the converter (while on Shore Power) and its 12v circuits in the RV?
Did you check all AC Circuit breakers and reset any if needed?
Did you check all the battery terminals? Make sure they are not cracked broken.
After we bought out Coach, we were using it one day and my 12v circuits stopped working. After careful inspection, noticed the positive House bank battery connector had a temporary repair connector (like the "cheap lead terminal" on the left below) that was cracked and the converter's protection fuses blew. It probably was breaking the connection/disconnected (from vibration) while we were in/using the Coach which was parked next to our house.
I had that battery terminal connector repaired with a permanent heavy duty connector and checked all the rest (having several re-done as well and crimped properly and insulated) by the local Interstate Battery Distributor. The only charged $60 for an hour's work and that included him driving to our house. I then replaced those the two fuses in the converter and all was good.
No issues since.
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