This is strange, i watched videos of people hitting monsters/enemies on horse and it always hit. Now i am riding a horse and for whatever reason, i cant hit the enemies. I even tried positioning myself beside the enemy and swing my sword and it did not hit. This is really annoying. Bows work however.
Mods used that adjust combat/horses
My race: Nord, not custom race

mods used:
Skyre
Morrowloot
monster wars v3
skyrim monster mod

everything was configured with BOSS.

And the strangest thing is, when i first started the patched game(1.6.89), i can actually hit monsters on horse. But after a few levels, i cannot hit anymore. This is so strange.

No problems here. I suspect it must be caused by the modding. I'm on the Xbox, so no mods, of course.