TypeError: $w(...).onReady is not a function

Hi, i followed this tutorial: Velo Tutorial: Hiding a Video Player When There Is No Video to Play | Help Center | Wix.com
and I am getting always getting this error.
I would really appreciate any help!

Thanks in advance!

It looks like there’s no dataset in this page with ID “Portfolio”.

Thanks for the answer!

That solved the problem, thank you so much!
I accidentally entered the Name of the Database.