Hello there[url=https://cdn.discordapp.com/attachments/902560216871239752/989591085506515074/Hellothere.gif],[/url] This is most likely caused by having a heavy grenade launcher equipped. They are currently disabled due to a bug.
Do you have a grenade launcher in your heavy weapon slot? If so, that is likely your problem. They currently have a damage glitch and have been temporarily removed from the game. Switch to a different heavy weapon and that should fix it.