Hi Nikko,
I installed the plugin Enable jQuery Migrate Helper and that seems to have worked! At least now the Avia builder loads, and muy changes to pages do upload. Thanks, Sergio

N.B. For your information, the plugin returned this mesage when I loaded my homepage for editing:
jQuery Migrate Helper — Warnings encountered

This page generated the following warnings:

https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_advanced_form_elements.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_colorpicker.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_colorpicker.js: jQuery.fn.size() is deprecated; use the .length property
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media_advanced.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media_advanced.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media_advanced.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media_advanced.js: jQuery.fn.live() is deprecated
https://www.yatstay.com/wp-content/themes/enfold/framework/js/avia_media_advanced.js: jQuery.fn.live() is deprecated

Please make sure you are using the latest version of all of your plugins, and your theme. If you are, you may want to ask the developers of the code mentioned in the warnings for an update.