I just tried this on a local instance and it worked just fine:
First computer on MacOS with DSS running, connected to "Wi-Fi Network 1"
Second computer on Windows 7, also connected to "Wi-Fi Network 1"
Ran "ifconfig" in my terminal to find the IP address of the Mac computer
Accessed the IP address from Chrome on the Windows computer, DSS showed up as expected
In your case, what does the second user see when trying to access the IP address? An error message? If so, which one?
While setting up DSS, did you get any warnings that might indicate that a remote computer wouldn't be allowed to access your Mac computer? Are you sure there's no active security setting that might trigger this behaviour (besides your firewall obviously)?