1. Have they port fowarded?

If not, they will have to use a UPNP tool like Portmapper (java tool), or Port Forward on their router’s gateway. If not, you can use a VLAN like RAdmin / Hamachi, or a service like portmap.io or PlayIt. Roblox uses TCP.

2. Are you joining on the right client?

Check with them to see if you are joining on the right client.

3. Are you joining on the right port?

You can change your server port in ORRH. If it doesn’t match the server, or if the server host has not set up that port to be port fowarded, you won’t be able to join!

4. Is there a firewall in the way (Either sides)

Check with the host to see if they have a firewall blocking connections to the Roblox program. If they don’t, check if you have one.

5. Are you on the right version of ORRH?

ORRH is still actively developed, albeit on pause right now. They might be on a outdated / newer version of the program, so check with the host.