I'm trying to make a Minecraft server, but it says it can't connect?

So I was making a server on Planet Minecraft, I got it all set up and I just needed to post it on there. However, when I was testing the connection it said I needed a different IP, as the one I was using was only for my house. So I was like "Ok no biggy, I’ll just get the other IP." When I found it, I typed it in, got the port, and when I tested the connection, it said "Failed to connect to your server. Please check your input." and I tried most of the things I could think of, but it didn’t work. I was wondering if anybody knows how to fix this?