Storefront 3 - Cannot complete your request

I experienced the 1st connection to a storefront store each day gave the user a
"Cannot complete your request" message

If they user clicked to logon again it is successful.
The eventvwr showed Event ID 17 for each failure.

Typically this is caused by AV locking a file on first connection. However AV was not the culprit in my scenario. The AV Exceptions for reference are

\inetpub\temp\IIS Temporary Compressed Files 

\Windows\system32\inetsrv\w3wp.exe 

\Windows\SysWOW64\inetsrv\w3wp.exe

\Program Files\Citrix\Receiver StoreFront\Services\SubscriptionsStoreService

To correct the issue I needed to change asp.net file change notifications.
Info from Microsoft here. https://blogs.msdn.microsoft.com/tmarq/2007/11/01/asp-net-file-change-notifications-exactly-which-files-and-directories-are-monitored/

The change required is

For .NET 4 or lower

·         HKLM\Software\Microsoft\ASP.NET\FCNMode  DWORD = 1

           HKLM\SOFTWARE\Wow6432Node\Microsoft\ASP.NET\FCNMode DWORD = 1

  For .NET 4.5 and Higher

            o   Starting with the Microsoft .NET Framework 4.5 and later

            versions, FCNMode can be configured by using the httpRuntime

            settings as follows: