After installing iProcess workspace (browser) on IIS, the client URL does not work. 

Symptoms:
- Action Processor URL returns expected response
- No error entries are seen in APLog.log
- When accessing iProcess Workspace (browser) URL, the below error is seen - 

Unable to establish a connection to the action processor
Verify the Action Processor is running and the configuration URL is correct

- Inspecting the network logs using browser dev tools, the action processor URL returns a 500 error code. 

Cause:
The HTTP runtime rejects the initial validation as .NET framework 4.7 is used

Web server: IIS

When using IIS 8.5 or 10 and configuring Action Processor with a .NET 4.0 App Pool, the below post-install step is required - 

If you are hosting the .NET Action Processor in IIS 8.5 or 10, and you want the Action Processor to run in a .NET Framework 4.0 Application Pool, you must open the web.config file for the Action Processor’s web site, and uncomment the following line:
<!--httpRuntime requestValidationMode="2.0" /-->

This is required because .NET Framework 4.0 disables switching off validation of HTML input (that is, it causes the Validate=false setting in ActionProcessor.aspx to be disregarded).

This article documents a cause of "Unable to establish a connection to the action processor " when the iProcess Workspace (browser) is hosted on IIS

https://docs.tibco.com/pub/ip-wksp-brwsr/11.9.0/doc/html/Default.htm#installation/Post_Installation_Configuration_.htm#postinstall_config_3040690405_1700250?TocPath=Installation%257CPost-Installation%2520Configuration%257CPost-Installation%2520Configuration%257C_____0