I did the same but with deepslate bricks and it says invalid multiblock configuration

Originally posted by @valkyrienyanko in #57

I am having this same issue on Texkit 4 modpack.

Invalid Multiblock Configuration. Build 3x3. Have tried using all polished deepslate, regular deepslate, and deepslate bricks. All are not working.

You are missing the block on top of the Forge Controller, as depicted on the mod page:

I understand that and I built it per the screenshot you attached, but it won’t let me place down the final block. When I do, it shows the ‘Invalid Multiblock Configuration’ text, as shown on the screenshot.

Try crouching, or just place a block next to it to use as a frame. You can build this entirely out of a 3x3x3 cube of Polished Deepslate (including the Forge Controller), and it is still valid