So those are circuit breakers. They should be self resetting if they trip but not always.
First check the circuit breakers. Test light negative on the negative post of the battery. Touch the positive probe of the test light to both posts on the circuit breaker one at a time. The light should come on with the same intensity on both posts. That tells you the power is getting through the breaker.
If you have power through the breakers then pick a light that your test light can access while connected to the battery. Maybe try a side marker light. Connect the test light ground to the negative on the battery. Now remove the marker light cover and pull out the bulb. Using the positive probe on your test light touch the two metal contacts in the marker light one at a time. You should get a light on one contact and no light on the other contact.
