Have you plugged in the cables well everywhere without dirt, the cables are not damaged and the Motu m2 has the latest drivers?

It is important to know that the Shure SM7B is very gain hungry. Often the gain of a conventional interface is not enough. So if you turn up the gain control on the interface, it starts to hiss. What can help is e.g. Cloudlifter CL1 or (cheaper) a FetHead Vib Tritonaudio. Unfortunately, you can't buy these at digitec. Important: These "gain boosters" can only be used if the interface is 48V phantom powering capable.