Answer:
The way Barry most efficiently would determine if the problem is with the power company or the sign itself is to attempt to switch on another device to see if it has power.
Explanation:
The first thing that Barry can do in order to determine if the problem is with the power company or the sign is to see if there are other electronic devices having problems with power in the place, if everything else seems to be working as usual then it is logic that is the sign which has a technical problem that stops it from working.