SANKY trailer

Hello all, I've been renovating my SANKY trailer which has been sitting outside for at least thirty years; and I plugged it into the back of the Landy and all the lights worked even the little white ones on the front but the indicators did not. I put a meter in the bulb socket and I'm getting a little charge but not enough to light the bulbs....before I pull the box off again is there a quick answer..

I would first check that you are getting turn light voltage from the NATO socket on the vehicle.
M - LHS
N - RHS
Then if that is OK check the earthing is good on each of the trailer earths for the turn lights.

OHHHHH that makes sense, I sure all the cables are good on the trailer and feel the problem is further back..the ends of the yellow cables in the Landy are Joined in the right hand rear light cover..So I'll check cables M and N
Thank you so much for your help...