I am playing the UniversIO modpack and whenever I drop items, they don't trigger pressure plates.
I looked online and couldn't find anyone else having same problem as me.

Tested it myself and it works just fine. I don't think there is a connection between ItemPhysic and this issue. Also note that not all pressure plates react to items laying on top.

@Velken (I'm also playing UniversIO) You probably need to modify your OpenPartiesAndClaims world config to have Protect Plates From Other: OFF (default hotkey: ' > "Player Config Menu" > "My Player Config" > page 3 > "Prot. Plates From Other"), otherwise pressure plates in claimed chunks won't work for automation. (It is indeed unrelated to this mod)