I have a fresh install of 2.1. After the installation, mautic runs OK from the original browser. If I try to access the domain from another location (another PC’s browser) the address bar shows: http://domain.com/s/dashboard and I get the browser error:
It's missing the index.php reference in the address bar after it comes back from the server.
So it works from the original browser where I installed it, and gives the error if I try to access from anywhere else.