My team and I have discovered that for iOS 13.1 updates and onward, Collector will not allow the user to log into an Enterprise Portal. If the user was already signed into the portal when the updated occurred they will be fine until they sign out. But after they sign out of the enterprise portal, they are unable to sing back in. They get an error message saying "Unable to Connect to Portal - The operation couldn't be completed. (kCFErrorDomainCFNetwork error 301). Has a bug and/or hot fix been requested for this? This could turn into a major problem for our users...
I know that there is a similar bug open for Explorer.
BUG-000125896 - After updating to iOS 13, Explorer for ArcGIS is unable to login to Portals configured with Integrated Windows Authentication(IWA) with the error kCFErrorDomainCFNetwork error 301
Thanks very much,