Why was the toon cancelled?

Because Demi Lovato lost her mind.

Demi was doing bad stuff and was practically kicked off Disney.

Demi had some issues including a eating disorder, cutting, and her inner demons. She went to treatment at Timberline Knolls for three months. She is doing a lot better now. She says it's still an everyday struggle but it's worth it. I hope my answer helped you.