Yes, this has happened to me before. Try the following:

•Restart the game
•Disable then enable the addon via menu or in-game but then change maps
•Uninstall the addon, then re-install it.
•Find any conflicting addons and disabling them when using this (try to uninstall addons that you don't use anymore or don't use anymore. If the addon then starts working after uninstalling one, that's the mod that probably conflicted with this.)

This is probably a restriction due to a glitch, nothing you can't fix without common sense. Hope any of the above works.