I'm in the same situation
I’ve already tried all the suggestions mentioned in https://kb.fenixsim.com/installer-issues , but unfortunately, none of them have solved the problem (MSFS 2024 MS Store).
In my system with the left click and drag the brightness of the lamps is adjusted (if you zoom in enough you will see that text DIM and an arrow on the lamp label).
With the right click the lamp test is done.
With left and right and drag you perform both functions: test and brightness adjustment.
Note that I use the "cokcpit interaction system" in "legacy"
The amount of detail on this plane is amazing. My congratulations to A2A.