Cant add modifiers

[ZevBellringer]

Describe the bug
A clear and concise description of what the bug is.
Running MC 1.20.,6 Modifiers cant be added to tool/weps. arm.

To Reproduce
place tool /weapon/armour with one free slot in anvil,

select and place in anvil modifier item that can be legally added to that tool/etc using 1 slot

nothing happens, modifier isnt added

Expected behaviour
should add modifier to weapon.

heres a new diamond pickaxe , trying to add directing mod to it. Nothing happens

i have 30 exp levels, but nothing can be added to any MT tool.

Screenshots
If applicable, add screenshots to help explain your problem.

[Flo56958]

@ZevBellringer is there a message in the action bar or the console when trying to modify?