[UPDATE] I had to move the texture packs OUT of my Minecraft texture pack folder, into downloads, for it to work. Very odd and lowkey inconvenient, but I suppose it'll work...
Usually I can just drag and drop .zip files and folders from my minecraft pack folder into the server's Resource pack, but now it's giving me a pop up and won't allow me to add any packs. I'm not doing anything different, and I even tried the same packs I've used in the past, and now they don't work at all. What do I do?
Here's the pop-up I'm getting 
