Unauthorized access and user access is denied errors while trying to access Portal for ArcGIS home page

Error Message

Unauthorized access and user access is denied errors are returned while trying to access the Portal for ArcGIS home page.

After upgrading Portal for ArcGIS from 10.9.1 to 11.3, the following errors are received:

In Portal home:

Unauthorized

In the Portal Administrator Directory:

Error 
The user Access is denied. does not have full control permission to the directory C:\arcgisportal\db.
Code: 500

Additionally, an anti-virus notification also displays similar to the following:

Use of application Microsoft Windows whoami has been blocked by your administrator

Cause

Use of application Microsoft windows whoami has been blocked by your administrator.

Portal for ArcGIS and ArcGIS Datastore call the command line tool 'whoami' on Windows by opening the Windows Command interpreter (CMD.exe) via a Java process.

Solution or Workaround

• Request your IT team to create an exception for "Microsoft windows whoami" in the antivirus application.
• Check the Solution or Workaround section of the following article: McAfee Endpoint Security Identifies JAVA.exe as a potential threat source in Portal for ArcGIS or ArcGIS Data Store