Unable to connect to WebAdaptor URL: https://<FQDN>/portal/webadaptor

Error Message

When accessing Portal for ArdcGIS or ArcGIS Server through ArcGIS Web Adaptor (Java), the Web Adaptor URL returns the following error:

Could not access any ArcGIS Enterprise portal machines. Please contact your system administrator.

Even if the Web Adaptor appears registered (or not registered) in the Portal Administrator Directory, attempts to configure or reconfigure the Web Adaptor using configurewebadaptor.sh fail with:

[arcgis@<machine> tools]$ ./configurewebadaptor.sh -m portal -w https://<FQDN>/portal/webadaptor -g https://<PORTAL_HOSTNAME>:7443 -u <PORTAL_ADMIN> -p ******** -a true
Unable to connect to WebAdaptor URL : https://<FQDN>/portal/webadaptor

Reviewing the external Tomcat logs (catalina.out) shows a decryption exception similar to:

“Could not decrypt: Given final block not properly padded. Such issues can arise if a bad key is used during decryption.”

The repetition of the “Could not access any ArcGIS Enterprise portal machines” message indicates that each request processed by the Web Adaptor fails.

Cause

One possible cause is an inconsistency in the Web Adaptor configuration state after an upgrade or rollback.

In some rollback scenarios, the Web Adaptor configuration file may reflect a different version state than the restored ArcGIS Enterprise environment. For example, the webadaptor.config file still indicates a newer version 

At this time, this behavior is considered an unknown scenario. The error presents on either the Tomcat or Web Adaptor side and has not been tied to a single root cause beyond.

Solution or Workaround

1. Validate versions (Web Adaptor and Tomcat):
   Confirm the ArcGIS Web Adaptor version matches the ArcGIS Enterprise version in the restored environment, and confirm the external Tomcat version is supported for that Web Adaptor release:
   
   • ArcGIS Web Adaptor 11.1 system requirements
2. Review the webadaptor.config file and replace if it shows a different version:
   Locate the Web Adaptor configuration file (webadaptor.config) for the Tomcat OS user and confirm the <Version> value. This configuration file is usually located in:

/home/tomcat_arcgis/.webadaptor/portal/webadaptor.config

3. If the config file shows a different version than the restored environment, for example, <Version>11.5</Version>, while running 11.1, replace the webadaptor.config files for both the Portal and Server Web Adaptors with version-aligned configuration files.
4. Reinstall Tomcat (fallback):
   If the issue persists, reinstall the external Tomcat instance. In this scenario:
   1. Reinstall the ArcGIS Web Adaptor as well.
   2. Redeploy the WAR files.
   3. Clear the Tomcat cache/artifacts, and 
   4. Re-run the Web Adaptor configuration.