I can't get my apple tv to reset, and stop flashing?

First try a ‘cold’ restart: disconnect from power for a minute or two.

If that doesn’t bring it back, then the unit may need to be restored.

Restore your Apple TV - Apple Support

Unfortunately, for the 4K model, you can’t perform this procedure yourself. If you have an Apple TV 4K, then contact Apple Support. They may ask you to bring it in, or mail it in.