Versailles erased the tooling behind Germany's old heavy guns

Why did Germany not revive its First World War 38-centimeter naval guns and update them?

The postwar dismantling of German arms production had destroyed much of the tooling and industrial system needed to build those weapons.

A gun design is more than a set of drawings. Producing it requires specialized machine tools, metallurgy, gauges, trained workers, and an established chain of suppliers. The Versailles settlement broke up much of the industrial system that had built Germany's earlier heavy weapons. The later navy therefore had to create new guns and production methods rather than simply restart an old line. Industrial memory and tooling were essential parts of naval rearmament.