Wordpress Civicrm -Uncaught ReferenceError: CRM is not defined for contribution page
I'm also facing this problem (CiviCRM 5.3.0, WP 5.6.1, Avada 7.2.1).
The CiviCRM-Javascript-Resources are not loaded at all.
Disabling the Fusion Builder (so working with the regular WP editor) for the page where the CiviCRM-shortcode is inserted gets the resources loaded and the payment form working.
We're still facing Avada layouts issues on the next page though. But at least registration and payment work now.