What I do is I download a pack for 1.16, then edit all the textures. In your pack.mcmeta i'm pretty sure there is a number, and change it to... six? I believe six. There are some tutorials for it.
You could have deleted the files or something. Make sure you are putting your packs into your "resourcepacks" folder. Sometimes I get confushed and leave out the s, so that could be the problem?