The fixed face of a sheet metal is the face about which SolidWorks unfolds sheet metal parts. It is set by the first sheet metal feature by default. However, that might not necessarily be the face you want to be fixed. To find out which face is fixed, edit the flat pattern feature.
A different face can then be specified in the properties.
If you’re still having trouble changing the fixed face, feel free to call Hawk Ridge Systems Technical Support at 877.266.4469 (US) or 866.587.6803 (Canada), or you can email us at firstname.lastname@example.org.