When my players try to drop items it says, you are not allowed to drop [ITEM] here.
", sans-serif">- OJ_Fireman
Kipx, is correct, check your world gaurd region flags.
I know world gaurd and world edit can be confusing, my moderator told me about this plugin and its been super easy since then
https://www.spigotmc.org/resources/wg-gui.57951/, it adds a GUI to world gaurd/world edit commands.