[Uhehner]

One step at a time.
Put ALL your DC circuit breakers on at the Main DC panel and see if things work.
Are your MAIN disconnect (big red rotary) switches on?
Turn the VHF power switch on and cycle all your dash switches and see if the VHF comes on.
If you have little rubber circuit breakers on the dash see if one popped up.
You now need a voltmeter with a 20 volt scale set to DC volts.
Follow the VHF power line back to where it's attached to a bus bar, switch or fuse and check the fuse.
Put the black lead on the black wire and the red lead on the red wire.
You should see over 12 volts.
Let us know the results.
The Marine Tech should warranty his work for over 30 days.
Capt. George