I created a squashed cylinder and am rotating it around its axis via:
local platform = script.Parent
while true do
platform.CFrame = platform.CFrame * CFrame.fromEulerAnglesXYZ (0.05, 0, 0)
wait()
end
But when my player jumps up on the rotating part, he does not spin or move with it. Why?

2 comments
all you are doing is changing the platform's orientation, like teleporting the platform a bunch of times. you could try BodyAngularVelocity https://developer.roblox.com/api-reference/class/BodyAngularVelocity
Friction*