Error in Admin Portal Web UI: " Error occurred while processing your request SkypeShield Access Portal has encountered an error."

When opening the Access Portal Web UI and facing this error:

Error occurred while processing your request
SkypeShield Access Portal has encountered an error.
Please send logs to support@agatsoftware.com
and you want more details, you can turn off this generic error with the following steps:
  1. Open IIS Console
  2. Browse the Admin Portal folder
  3. Edit the "Web.config" file
  4. Change <customErrors defaultRedirect="~/pages/errors/genericError.html" mode="On" /> to <customErrors defaultRedirect="~/pages/errors/genericError.html" mode="Off" />
  5. Open the Admin Portal Web UI to see the full error