Sounds like an ACL permission issue. Check ACL at your Org level in your WC system.
Click Organization Icon, select Utilities, click Policy Admin.
In the Policy Admin pop up , open the Default domain for your system, click PDM domain, then click on the View command button. click Access Control tab.
Look for WTChangeOrder2Type ACL and see if the OOTB ACL PTC created for Change Notice were deleted. If yes, add ACL for your Principal for the appropriate State. You require a min of "create" permission to create a new Change Notice.
Hope this helps...