It can happen, especially after major updates, that some basic Textures stop working. The solution is quite simple. You just need to hold down T on the keyboard for 5 seconds in the resource pack menu (shown below) and then press ‘Done‘. Once that’s done, the texture packs will be as good as new!
ATTENTION: If you have added some textures that ARE NOT present in the base modpack, these could be the cause of the problem, so try disabling them first.
