Facebook Messenger (Mobile) Issues

I have been having issues again with FB Messenger while I am on mobile. I can only send FB Messages when I am on WiFi. I have the Cellular Data toggle turned on for it too but it does not do anything. I do not know why T-Mobile/Sprint is causing this issue. It happened with my Samsung too, especially with Text Messages. But mostly with FB Messages. I have never had this issue for the entirety of my service with T-Mobile. Ever since they merged with Sprint everything went haywire. I can not send messages over FB unless I am connected to WiFi...