Citrix Director has been upgraded to a recent version (we observed the issue with different upgrade paths 2402 -> 2507, 2511).
The issue occurs in the environment where the default IIS Application Pool location has been changed to a different drive (Physical Path). By default, Director is installed on the C drive.
Administrators and Help Desk users are not able to log in to Director.
The error displayed:

Assembly binding contains a reference to the C drive, which is not valid in a scenario where the Director files are located on a different drive.
How to check current Director location:


How to resolve the issue:
Example:
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<!-- autogenerated bindings are in a different file -->
<linkedConfiguration href="file://C:\inetpub\wwwroot\Director\Bin\WebService.dll.config"/>
</assemblyBinding>
Administrators and Help Desk users are not able to log in to Director.