setting up XP farm and the spikes dont seem to work like they say they do

Generally this means either, a mod is interfering with the xp dropping, OR a mod that protects an area(think ftb chunks, or minecolonies, etc) is preventing the fakeplayer from acting properly.

I am not in a protected area, what would be the best way to debug ?

Another possibility that ive seen, is some block/machine nearby intercepting the xp, like a absorption hopper, or something else.

I have an absorbtion hopper and it is not getting any xp saddly