IIRC “3D Printed” houses are falling apart due to lamination issues. That said, I think it's a solvable problem, though it will take awhile to sort out the issues.

You'd probably have to invent a new type of concrete first. You can add resin binders to concrete to make wet concrete somewhat stick to drying concrete but it doesn't work very well. The drying concrete tends to pull the moisture from the wet concrete which ends up interfering with the curing of both sides.

The main issue with 3d printing concrete is more of an inherent issue with how homes settle over time. Unless you are building on bedrock or you're driving a massive amounts of piles for the foundation, structures will move and settle over time. This is why brick and mortar have been around for such a long time, the mortar gives the bricks enough flexibility to accommodate movement.

Concrete lacks this flexibility and will crack and crumble apart unless you reinforce it with rebar. Rebar gives concrete tensile strength, distributes weight across the whole structure, and holds cracked pieces together. So really any 3d printed home that isn't reinforced somehow wont last very long.