Maybe you didn't have the connectors screwed on all the way and flush with the assembly?
Did you install the connectors on the cable and the jumpers or did you buy them already installed?
Use a volt/ohm meter set on continuity
to check the connections on the jumpers first and then your main coax cable disconnected from the antenna. The cable should show "open
" when the shield is tested to the center connector to the shield and closed when testing center to center and shield to shield. While testing them, move them around to see if you get intermittent contact. Jumpers are always
suspect in a feedline problem!