65 Barracuda gauge problems

OK, What looks like a condenser is a noise suppresion cap' . The original limiters mechanical points would make a pop noise in radio speaker. Since a solid state regulator doesn't make a pop noise , you wouldn't need the cap' . I dont know what you bought so... Anyway, There is one small problem. That little black wire on the cap' had a male spade terminal that was poked into the contact slot along with the male spade on the limiter. Delete the one and you have a loose fit and probable lost connection.
There are members here that will tell you to solder those female contacts in the boards to the copper foil on the boards, and that fine I suppose.
Bottom line, what you have right now is loose connections.
There have been cases where poking around with a tester showed it working and once installed it didn't work.
There is one solid state limiter that comes with ring terminals and 3 small screws to attach them at those slots to solve these issues for the end user.
Some vendors just sell parts. Others promote happy moparing whether that includes selling a part or not. Good luck