Why do I get error message ‘Unable to start debugging on the web server. The debugger is not properly installed. Run setup to install or repair the debugger. Would you like to disable future attempts to debug ASP.NET pages for this project ? ‘

If someone has run a lockdown or other security tool on the Web server, the
DEBUG method may have been removed.

Go into IIS manager to the Web application’s properties and Directory >Configuration (button) > Mappings > Application mappings.
Check that for .aspx extensions, you allow GET,HEAD,POST,DEBUG

Of course you need to be a member of the Debuggers group on the remote server.
To resolve error

1. Right-click the Project Name in Solution Explorer, and then click Properties.
2. In the left pane of Properties, click to select Configuration Properties.
3. Click to select Debugging.
4. In the right pane, change the value of Enable Unmanged Debugging to True (on the drop-down list).

For more details refer PRB: Error Message: Unable to Start Debugging. Unable to Start Program …