The pack can be found here on Curseforge. I suggest using Prism Launcher. Other launchers will work fine, but the fix below is Prism specific. Don't neglect setting up java arguments. Generic pack install instructions and java args can be found in the description of my old 1.12.2 pack's description.. Unfortunately, there's an issue with negotiating the Mojang Auth server specific to this pack. Changing your Java 8 version fixes it...

Setup Notes

• We'll be playing with just the two of us. If you want to play with someone else, create an FTB Team from the upper left menu. Then once your teammate has joined from the same Members menu, you can use "/cave invite playername" to add and teleport them to your hole.
• ~ (Grave/Tilde) is does ore excavate or vein mine. However, it's double bound with the Morph mod, which isn't listed. you'll have to hit "Esc", then click "Mod Options", then type "Morph". You can rebind the morph selection wheel key there to fix things. Alternatively, just rebind the Excavate key.

Rules to Join the Server

1. Be a member of the Late Discord Server where almost all the communication and announcements will be. If you're reading this, then you probably already are. If a friend has linked you this, then you better join. It's not just a good idea. It's the law.
2. @me to tell me your Minecraft name and that you're joining, just as a courtesy.
3. Respect others' claimed chunks. Don't try break or steal stuff in another team's claimed base... If that's a thing.
4. PvP is enabled! Team up, compete, troll, whatever. Just keep it in moderation. Basically, don't do enough in a day that could be described as "harassment" or "irrecoverable".
5. Manage your lag. IE: entities, mobs, animals. Turn your laggier contraptions off when you're not online or design them to stop when full.

First test by launching Stoneblock 2, and opening the multiplayer menu. Does it look like this?

If so, then you have the bug.
Here's the 11 step fix in 2 easy pictures...

Okay, enough messing around, what's the IP?

You're on it, ya derp. Just type this web domain 'sb2.ez2.us' into your game and go.