Something very weird happened to me last week, I could not run any Sitefinity 11.1 application from the new SitefinityCMS.exe Project Manager. Chrome kept reporting a refused connection as you can see in the image below
The weird part is that I have at least 10 different versions of Sitefinity on my machine from 6.x to 11.1 with their own Project Manager and all work fine.
I could run the 11.1 project from Visual Studio 2017 with IIS Express in Chrome with no issues. It is only through the Project Manager that could not with "connection refused" error.
Also running the same site in regular IIS on Windows 10 works just fine.
That was a tough one to figure out.
After spending few hours, I was able to figure it out by coincidence. The latest update of Windows made a serious change to the Windows Defender application on the machine by enabling the Ransomware protection "FOLDER" protection. This feature causes some folders NOT to allow changes to its content until you add the folder to the "ALLOWED" list.
Adding the Project Manager folder for 11.1 or turning off the Folder Ransomware protection feature will enable Chrome or any other browser to start the Sitefinity application with no issues.
Hope this helps someone out there.