"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
\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: