He's saying "the show will never hit its groove." in this case, it means.. it will not find success. However, it is an informal saying that implies a few other things; sequence, rhythm, flow or lack thereof. so in this case, he thinks because there are only 6 shows, it will not have enough chance to do well where things can easily sync up. Im assuming like writers, viewers, publicity or whoever this is about. A few other tangential examples. a sports team working really well together -- they hit their groove. or say there is a comedian and they get a few jokes in and one after another after another are funny, you could say the show hit its groove. or she/he hit their groove.