Portal for ArcGIS: The user may have been deleted or you may have entered an incorrect URL

Error Message

Attempts to delete a member in Portal for ArcGIS fail with the following error message returned:

Error:
The user you requested cannot be found. The user may have been deleted or you may have entered an incorrect URL.

Cause

The portal index is corrupted, causing the index count for users to not match the store index count.

Solution or Workaround

Warning: 
Esri recommends performing the reindex operation during system maintenance or downtime, as the operation takes some time to finish. During this time, portal content and search operations are unavailable and the index service may not respond correctly to index queries.

1. Navigate to the Portal Administrator Directory as an administrator using the following URL:

https://<machine>.<domain>.com/webadaptor/portaladmin

2. Navigate to System > Indexer > Index Status.
3. If the Count in store values do not match the Count in index values for users, navigate to System > Indexer > Reindex.
4. For Mode, select User from the drop-down list.
5. For Format, select a response format from the drop-down list.
6. Click Reindex.