I just got my TV today and while it’s a nice TV that performs very well, it does not support casting from mobile devices as claimed in the feature description:
“Browse content on your phone or tablet and play it directly to your VIZIO Smart TV. Enjoy true multi-screen viewing with Second Screen-ready mobile apps like Netflix® and YouTube®”
Hi there. Check the back of the TV and make sure it’s the correct model number.
If so, it should support that feature according to the Vizio site.
The manual is on that page and the information on doing it is on page 50.