Only one full-beam working

I have a 4 light grill, both my dipped (outer lights) work fine but when I switch to full beam, neither of my passenger side lights work.

The bulbs are ok, and it looks like the +ve wire has current to it. How can I trace this problem? Could I run a wire from the -ve straight to the battery, would that show if the -ve is at fault?

Check all the fuses, as there is one for each light bulb 2 for high and 2 for low.

Then check that the ground is good on both bulbs.