1.17.x, 1.18.x, and 1.19.x blocks (Ex. Amethyst, Tuff, Deepslate) aren't added into DiamondFire yet. All blocks from the versions listed turn to stone because the server doesn't know what these blocks are. The server runs on Minecraft Version 1.16.5... So, you can only use blocks from 1.16.5 and older.
Also, why did you post the same thing in two areas