Unable to configure web adaptor when WebContextURL does not match portal access URL

Description

When configuring the ArcGIS Web Adaptor with Portal for ArcGIS, the configuration fails with the error:

“Unable to configure Portal for ArcGIS with the web adaptor”

Portal may still be accessible directly using the internal URL and return an HTTP 200 response, but the web adaptor configuration does not complete.

The error may also be observed in logs or during repeated configuration attempts.

Cause

This issue is not related to credentials, firewall configuration, or installation issues and is commonly seen in environments using reverse proxies or load balancers.

This can occur when the WebContextURL configured in portal does not match the URL used during web adaptor configuration.

In environments using a DNS alias, reverse proxy, or load balancer, Portal expects requests to match the configured WebContextURL. Using a different URL (such as an internal machine URL) during configuration may cause the request to be rejected.

Solution or Workaround

Ensure that the URL used during web adaptor configuration aligns with how Portal is intended to be accessed. 

• Review the WebContextURL in the Portal Administrator Directory under System > Properties.
• Ensure that the URL used during configuration matches the WebContextURL  
• If using a DNS alias or reverse proxy, ensure the configuration follows supported workflows for updating the organization URL 
• Ensure that the external URL is reachable and resolves correctly.

After aligning the URLs, reconfigure the web adaptor.