After configuring ArcGIS Web Adaptor with Portal for ArcGIS, Portal for ArcGIS cannot be accessed, and the following error message is returned:
Error: Failed to get administrator token from Portal. Please verify that the Portal URL specified can be accessed successfully.
Use either one of the following workarounds to resolve this issue.
Configure ArcGIS Web Adaptor with Portal for ArcGIS using an FQDN with the port number included
Refer to ArcGIS Enterprise: Configure ArcGIS Web Adaptor from the configuration web page for the steps to complete this. The format of the FQDN used in the Web Adaptor configuration page is as follows:
Reinstall and configure ArcGIS Web Adaptor