If it’s the dash light that’s not working it’s quick and easy to test the bulb. Remove the two screws and swap with the neutral bulb. It could be related to your JNS install but I’d check the bulb first since it’s so easy. There might be a metal post on the bottom of the assembly with a cotter pin that you have to remove, but I think that’s only on the back of the speedo assembly, not the indicator assembly.
I’ve had to replace quite a few of those bulbs, so I’m now replacing them with cheapo LEDs.
And welcome to the forum!