Build refuses to work when an entity is created

I am working on an "end update" mod and I have recently added a living entity (I do not know how to use Java). When I try to run the program, I get this error, which opens in the workspace. 

"One of your main mod files does not compile properly"

Then, it gives me two options:

Regenerate Code 

Ignore Error

Regenerate code does nothing and I have tried all techniques on MCreator's forum, including deleting the Gradle folder. Please Help. I want to release this mod in the future.