Adding Constraints to Sketch in Spaceclaim - Ansys

Hi, I'm having the an issue where the 'Sketch' ribbon on Spaceclaim is missing. I need to constraint my sketches and it's not possible to add them from the Design time. I tried adding them from the File -> Spaceclaim options -> Customize-> Ribbon -> Sketch, but the tab appears for an instant and then disappears.
Any help would be appreciated.