Engine lid earth

I have 360 spider and the third brake light is not working, I cleaned all contacts still nothing. I was testing the ground and it appears the entire engine lid has no earth connection.
Do these lids just ground via the hinges or is there a separate earth strap?

 

So they only earth when the lid is closed- through the latch itself?

 

I believe the positive runs through that connection, the earth cable is looped under the brake light bracket bolt on the lid. I cleaned this also but I am not getting any ground from anywhere on the lid. I am getting power through that contact