Gary, I'm trying to see if any users are having the same issues as us. I have a couple questions for you:
Is your Portal behind your firewall or public facing? Ours is behind our firewall
Are you using CA signed certificates or domain signed ones? We are using domain signed ones.
What version of ArcGIS Server and Portal for ArcGIS are you using? We have Server 10.2.1 and Portal 10.4
Is your Portal federated? Ours is not.
I've moved most of my questions to the Beta discussion site. https://community.esri.com/groups/explorer-beta I highly recommend getting on it and testing new versions of the app before it gets put out for general consumption.