Cannot change or add attachments to guns

I'm having an issue where I cannot change or add new attachments to guns. It makes the noise where you equip a new attachment but it doesn't actually equip it. So far this has locked me out of using both the m240l and the nvo-228e. I cannot add or change any attachments on both of those guns in any class at all. I'm just stuck with the attachments that were already on it when the bug started. And the m240l I've really been enjoying but now I can't change any attachments on it.