Error loading page, error was: error details: Forbidden

Took a long time to get app support configured correctly on our Project Server 2016 farm. But finally got apps running from the store, have tested other apps and they work fine, but Bulk-Edit is not functioning correctly. When I click on it, it pulls up the spinning wheel (Loading) and at the bottom I get the following error:

Error loading page, error was: error
details:
Forbidden

Have gone through all of the security articles and everything seems to be set correctly, not sure what else to do from here. Have had a client requesting the bulk Edit app for a long time and now that I have it close, I am trying to figure out this last piece. Any help would be great.