I need help! I didn't get my credits!?

I completed two custom challenges today for firefight matchmaking. I was doing the custom challenges because of the weekly challenge being for fierfight matchmaking. After I completed the challenges I turned them in and I let the time run out. After the time ran out I didn’t recieve the credits. I want to know why I didn’t get them. I know that it has been at least 30 minutes after the time ran out and I still have the same amount of credits I had when I quit playing for a while. Can anyone help me find out why I didn’t earn my credits. I just want to know because I wanted to use more custom challenges while I continue to complete the weekly challenge.