Credit gains in campaign with silver xbox live account

I’ve been playing reach since it came out, beat it on legendary and even played online multiplayer. Now I seem to have an issue with gaining credits during the offline campaign(while connected to live so i can get challenges and what not). The credits at the end of the level are only given to me for completing the level and none of the commendations i’ve been getting are giving me credit points to rank up. has anyone else been having this issue?