Since I am using a translator, my English may be unnatural. sorry.

This may be a rudimentary and ridiculous mistake, but the texture and model of the block will appear as black and purple blocks. Also, the name of the block item is displayed as Air.

public class TestBlock extends Block{
	public TestBlock() {
		super(Properties.create(Material.WEB, MaterialColor.WOOL).hardnessAndResistance(2.0F, 3.0F).sound(SoundType.CLOTH));
		setRegistryName("test_block");
	}
}

public class TestBlockItem extends BlockItem{
	public TestBlockItem() {
		super(new TestBlock(), new Item.Properties().group(DepressionMod.DEPRESSIONMOD_TAB));
		this.setRegistryName(new TestBlock().getRegistryName());
	}
}

@ObjectHolder(DepressionMod.MOD_ID)
public class DepressionModRegistry {
	@Mod.EventBusSubscriber(modid = DepressionMod.MOD_ID, bus = Bus.MOD)
	public static class Register {
		//Blocks
		public static final Block TEST_BLOCK = new TestBlock();

		//BlockItems
		public static final BlockItem _TEST_BLOCK = new TestBlockItem();

		//TileEntities
		//public static final TileEntityType<RedstoneCapacitorTileEntity> CHARGED_CAPACITY_TILEENTITY = TileEntityType.Builder.create(RedstoneCapacitorTileEntity::new, REDSTONE_CAPACITOR_BLOCK).build(null);

		//ItemRegistry
/*		@SubscribeEvent
		public static void registerItems(RegistryEvent.Register<Item> event) {
			final Item[] items = {
				new SilverIngotItem()
			};
			event.getRegistry().registerAll(items);
		}
		*/

		//BlockRegistry
		@SubscribeEvent
		public static void registarBlocks(RegistryEvent.Register<Block> event) {
			final Block[] blocks = {
					TEST_BLOCK
			};
			event.getRegistry().registerAll(blocks);
		}

		//BlockItemRegistry
		@SubscribeEvent
		public static void registarBlockItems(RegistryEvent.Register<Item> event) {
			final BlockItem[] blockitems = {
					_TEST_BLOCK
			};
			event.getRegistry().registerAll(blockitems);
		}
	}
}

 

Thank you. That way I was able to solve it.