UPDATED: October 15 2015
The "Lock Template" button present on the "Invitation Template" page serves more for internal iPerceptions use, so please refrain for clicking this button unless otherwise instructed by your iPerceptions representative.
The template will be "locked" whenever a customized invitation is currently implemented for a particular survey, instead of one of the invitation templates currently available on the portal for all iPerceptions plans.
The ability to use a customized survey invitation for your research is available with a subscription to our Project Services, starting with our Enterprise plan. Click here to request more information about our Enterprise plan, and to learn more about our Project Services.