Delete User Preferences Files.
Make sure "Hidden Items" is checked if the "ProgramData" folder is missing.
Go to the folder below and delete all the files and folders in it. Upon relaunching, GibbsCAM will rebuild everything that is needed.
For Gibbs 14.0.15 or older:
C:\Users\UserName\AppData\Roaming\3D Systems\GibbsCAM\XX.X.XX
For Gibbs 14.0.21 or newer:
C:\Users\UserName\AppData\Roaming\CAMBRIO\GibbsCAM\XX.X.XX