Error: Unable to display RD Web Access

I'm trying to configure our RD Web Access page through the F5. When the page loads I'm getting an error message;

 

Error: Unable to display RD Web Acccess.

 

It does mention Enhanced security configuration on the page but I don't know where that would be coming from. On the RD Web server it's disabled.

 

Anyone seen this before or have suggestions?

 

Thanks

 

Chris