My custom blocks aren't showing up

Hello,

In my addon, everything but the custom blocks are working. My custom recipes, mobs, and items work fine but the blocks don't show up in /give or in the creative menu. Their crafting recipes obviously don't work either.

I'm using 1.14.60 with experimental features, cheats, the behaviour pack and the resource pack enabled. I'm also using the latest official release of MCreator.

{
  "format_version": "1.14",
  "minecraft:block": {
    "description": {
      "identifier": "minecraft_ultrahard:compressed_cobblestone",
      "register_to_creative_menu": true,
      "is_experimental": false
    },
    "components": {
      "minecraft:map_color": {
        "color": "#392923"
      },
      "minecraft:destroy_time": {
        "value": 1.5
      },
      "minecraft:explosion_resistance": {
        "value": 15
      },
      "minecraft:friction": {
        "value": 0.6
      },
      "minecraft:block_light_emission": {
        "emission": 0
      },
      "minecraft:flammable": {
        "flame_odds": 0,
        "burn_odds": 0
      }
    }
  }
}

Here is the code that MCreator shows when I try editing the block.