Potion effect does not apply

That doesn't make sense.

I removed all plugins, applied only ModelEngine-4.0.5F, and ran the server Similarly, when using "/meg disguise", the potion effect is not applied

The version I used is paper-1.20.1-196

try this "/effect give name minecraft:jump_boost 5 5"

I'm encountering the same issue. It seems like NMS is mishandling it. Effects like poison, healing, and speed are being applied to the player, but some, like jump boost, aren't functioning correctly