I made an  xp farm where the mobs would spawn on a platform, and be pushed by pistons into water to carry it into the grinder, but the spawner just  says insufficient light level. When I checked the light it is ON ZERO is it just me who has this problem

what type of xp farm?

Don’t worry it works now.  the sp sense spawns the skeletons into water and then they get washed to the hopper floor

 i realised that the spawner had to be above the water to work