Importing any .mcaddon file causes the game to crash

I use .mcaddon files to import 3D models from Blockbench into my worlds. This worked perfectly, until today. I installed a new .mcaddon file to import a new entity, and the game crashed as soon as I clicked on the .mcaddon file. This resulted in a red screen (same red as the Mojang logo screen), and then the game crashed. I assumed this could just be this pack, so I deleted a resource and behaviour pack of a previous .mcaddon file that did successfully download only yesterday, and when I tried to redownload this one, the same thing happened. Please fix this soon!