Verify that you have:
1)Cleared (or renamed) any .msnbin files from your multiplayer/cooperative folder
2)Opened port 28000 TCP and UDP, as well as 28100 TCP (that latter is the downloader port)
3)Verified that you see those ports listed in the "Network" tab of the RoF settings
4)Change the Server name to something different.
5)Clicked the box to "Use external IP"

After doing that, try launching the server, and once the mission is fully loaded alt-tab out of the sim and visit the following URL: http://www.canyouseeme.org/ and check both ports 28000 and 28100 and verify that you see this for each port:

Success: I can see your service on (your ip) on port (28100) Your ISP is not blocking port 28100
Success: I can see your service on (your ip) on port (28000) Your ISP is not blocking port 28000

If you do all of the above steps, and the ports check OK, you should be good to go.

Nice summary Eco - thanks!

S~

Gunny

Just replying, so I can find it later, someday, when I need to worry about it.  ::)

Good stuff :) I'll add it too