No 12 volt power. What to check.

My money is Bad ground from The battery.

We had similar issue on way to Florida ... the ground connection from the batteries was rusted and not a clean contact.

westend wrote:
The circuit breaker between the battery and the distribution panel. It will be close to the battery and may look like a small metal can. ....

That would be my bet too. Mine is somewhat hidden in the font passthrough inside a wood enclosure.

Could you have hooked it up backwards? If so then you blew the reverse polarity fuses on the fuse panel or if it's a PDI converter they will be on the power supply itself.

YES, an automotive fuse can look OK but still be blown. That's why most of us carry a digital volt/ohm meter. Just $8 at most stores.

I do hope you have a meter so you can start running down the 12v's

The battery disconnect is in the "on" position. Found two 30 amp fuses in the area of the battery, both were good/not blown. One went to the motor for the landing gear, the other one disappeared into the wall of the basement.
Can an automotive fuse look ok but still be blown?

Battery disconnect?

The circuit breaker between the battery and the distribution panel. It will be close to the battery and may look like a small metal can. Some have a reset button. You may also have a blown fuse in that location. It is indicative because as the converter tried to charge the deceased bad battery, amperage may have risen beyond the rating of that circuit breaker or fuse.