IIS - one website is working but my other website can't be found.

For two IIS sites on the same server, when one works and the other “can’t be found,” focus on binding and port/SSL conflicts and what is actually listening on the ports.

Work through these checks in order:

1. Confirm the second site’s port is actually listening
   • Open an elevated command prompt and run:
     • netstat -ano | find ":80" (or the port used by the second site)
   • If nothing is listening on that port when the second site is started, IIS may have failed to bind (for example, due to SSL or URL reservation issues).
2. Check for SSL/HTTPS binding conflicts
   • If the second site uses HTTPS, verify there is no SSL port conflict:
     • In IIS Manager, for each site:
       1. Open the site’s Bindings….
       2. For type https, confirm the Port (usually 443) and Host name are unique or correctly configured.
   • If multiple sites share the same IP and port 443 with SSL, they must be configured correctly for SNI or dedicated IPs; otherwise only one will respond. SSL conflicts can prevent a site from starting or from serving traffic.
   • If using wildcard certificates and multiple sites share the same IP/port, changes to one site’s certificate binding can affect others because http.sys binds certificates by IP/Port, not host name. Use appcmd.exe for binding changes or deletions to avoid breaking other sites.
3. Verify HTTP.sys URL reservations and SSL cert bindings
   • From an elevated command prompt:
     • netsh http show urlacl – confirm there is no conflicting URL reservation that blocks the second site’s URL pattern.
     • netsh http show sslcert – if the second site uses HTTPS, ensure the port (for example 443) has a valid SSL certificate binding and that it matches what is configured in IIS.
   • If the port is not listed, http.sys is not listening for SSL on that port, and the site will not respond over HTTPS.
4. Check for port conflicts with other services
   • Ensure no other service (for example, another web server, SSRS, or a management service like WMSvc) is bound to the same IP/port combination the second site is supposed to use.
   • If another service already owns the port, IIS cannot bind the second site.
5. Review IIS and HTTPERR logs
   • IIS logs (by default under C:\inetpub\logs\LogFiles\) and HTTPERR logs (under %WinDir%\System32\LogFiles\HTTPERR) can show whether requests are reaching the server and what status codes are returned.
   • If the second site never logs requests, the DNS/port forwarding may not be reaching the server, or another site is answering instead.
6. Validate DNS and host headers end-to-end
   • From a client machine, run nslookup yourdomain.com and confirm it resolves to the server’s public IP.
   • In IIS bindings for the second site, confirm the Host name matches exactly the domain being requested.
   • If both sites share the same IP and port (for example, HTTP on port 80), they must differ by host header (host name) to be distinguishable.
7. Confirm firewall/NAT rules match the second site’s port
   • If the second site uses a non-standard port (for example, 8080), ensure:
     • The firewall on the server allows inbound traffic on that port.
     • The router/NAT forwards that external port to the server’s internal IP and port.

If, after these checks, the second site still cannot be found, focus on:

• SSL/HTTPS conflicts (especially if both sites use 443 on the same IP).
• http.sys not listening on the expected port (no entry in netsh http show sslcert or netsh http show urlacl).
• Another service already bound to the same IP/port.

References:

• Error message when you try to start the Microsoft Forecaster Web site: "IIS was unable to start the site. Another site may be using the port you configured for this site. Please select an unused port."
• Change the IP/port binding of a site that is configured to use a wildcard certificate causes other sites on the same server to fail
• Handling URL Binding Failures in IIS Express
• Troubleshooting Internet Information Services
• Diagnosing failures with remote administration
• Set up SSL on multiple web sites in IIS with shared configuration
• http.sys not listening on port 443 for some reason my certificate is not working for ssrs - Microsoft Q&A