You're probably trying to record in a resolution that the 120GB
CineSSD won't allow as it has a lower max bandwidth to the bigger cards.
The only ones you can use with the 120GB are:
CinemaDNG 4096x2160 and 3840x2160 @ 23.97/24/25/29.97
ProRes 422HQ 3840x2160 and 5280x2160 @ 23.97/24/25/29.97
ProRes 4444XQ 3840x2160 @ 23.97/24/25/29.97
If you want higher frame rates and different res to those, then you need to buy the 240GB or 480GB sticks.
HTH