custom model data changes?

I updated to 1.21.6 from 1.21.1 and changed my pack.mcmeta to 63 but the textures are not loading in game anymore. Did they change the way textures are loaded?

I've also noticed the old command no longer works /give <p> minecraft:paper[minecraft:custom_model_data=1]

Any help would be much appreciated - Thanks (please ping me)