I have generated a blockstate .json file in src/generated/resources/assets/multicolored_dragon_mod/blockstates/multicolored_enderdragon_egg.json . My registration code in MyMod.java is as follows:

public static final DeferredRegister<Block> BLOCKS
    = DeferredRegister.create(ForgeRegistries.BLOCKS, Constants.MODID);
public static final DeferredRegister<Item> BLOCK_ITEMS
    = DeferredRegister.create(ForgeRegistries.ITEMS, Constants.MODID);
public static RegistryObject<Block> DRAGON_EGG_BLOCK
    = BLOCKS.register(Constants.EGG_ID, ColoredEggBlock::new);
public static RegistryObject<Item> DRAGON_EGG_BLOCK_ITEM
    = BLOCK_ITEMS.register(Constants.EGG_ID,
    () -> new BlockItem(
        DRAGON_EGG_BLOCK.get(),
        new Item.Properties().rarity(Rarity.RARE)
    )
);

// ...

public MyMod() {
// ...
    EntityRenderers.register(EntityType.ENDER_DRAGON, ColoredDragonRenderer::new);
    MinecraftForge.EVENT_BUS.register(this);
  
    BLOCKS.register(FMLJavaModLoadingContext.get().getModEventBus());
    BLOCK_ITEMS.register(FMLJavaModLoadingContext.get().getModEventBus());

    FMLJavaModLoadingContext.get().getModEventBus()
        .addListener(ModPacketHandler::register);
}

Yet I get the following FileNotFoundException warning on load:

[05:21:54] [Worker-Main-14/WARN]: Exception loading blockstate definition: multicolored_dragon_mod:blockstates/multicolored_dragon_egg.json: java.io.FileNotFoundException: multicolored_dragon_mod:blockstates/multicolored_dragon_egg.json

Looking with a debugger, I found that in SimpleReloadableResourceManager::getResources, this.namespacedPacks doesn't contain multicolored_dragon_mod, which is very strange... any help would be appreciated.

Edited March 9, 20223 yr by Will Bradley
Changed dummy to real world variables

you didn't make the blockstate json. X.x

Just because you register a block, doesn't mean Minecraft generates those model & blockstate files.

Quote

I have generated a blockstate .json file in src/generated/resources/assets/MODID/blockstates/my_blockstate.json

 

show the Model, why did you replace your Mod id with 'MODID'?

src/main/resources/assets/MODID/blockstates/my_blockstate.json

why aren't you using this one?    I personally tend to do my own support files, and this location, from within the main folder. 

Are your other blocks working?  also, I don't see the name of the 'block' that you the file is meant to match.

Sorry, I tried to anonymize it by replacing my real names with dummy variables, but I wrote it at 5 AM so it was all screwy. My bad.

It's fixed now.