I am imported step data from UG that is a solid and when it comes into catia it is a CLOSED_SHELL #96. Is there a way to either make it a solid or a way to change the import process.
I suspect that the translation is leaving a gap between the surfaces somewhere. That's probably why the import didn't give you a solid in the first place.
You may wish to perform an Examine Geometry check in UG prior to exporting the STEP file from UG. Look for large edge tolerances or angle tolerances & see if they exceed CATIA's modeling tolerance(s). Another option is to play around with the STEP export settings in UG to see if that makes a difference.