Entities won't work and stop my test from loading at all!

I have made my entity in blockbench, it is on the proper version, made for it too. Yet whenever i implement my entity into my mod, it NEVER launches. The app also NEVER allows me to apply the animations like this clearly outdated website shows, it tells me to add an animation to each individual body part rather than the animations i created in Blockbench and even exported. WHAT IS HAPPENING? I have never had these issues before when I made entities on older versions...