Thanks for replying to this. I finally resolved the problem by going to Safari settings on my Mac laptop (not the iPad), and under Content Blockers additing identity.api.navigraph.com and setting this to “off.” I was then able to log on to charts.navigraph.com on Safari on both the Mac and iPad as well as on the iPad app. So all is well, but the absence of any useful error message made tracking this down an exercise in frustration.