Texture Pack will not load

I have a custom texture pack that I use that is modified directly from the vanilla resource pack. I have been using it for well over a year and was using it last night. I came back and now the texture pack will not load. I keep getting an "Appearance is taking a long time to load. Proceeding with world generation" I attempted to put this on my computer which has more than enough specs to handle how large this world is. Nothing.

I have gotten the updated version of the texture pack and have the same issue. I have tried to thin out the bulk of the texture pack, nothing. I have been working on this world for over 3 years and have put hundreds of hours into it. I need this texture pack to work. I do not understand how I can play the same game, 3 hours later, no updates, and it no longer works.