Hi,
I have similar problem and I found something in this support page that resolve the situation with the blank page in advanced layout editor.

Go to the top right of the page your are editing and click in the screen options (near help button) then select or chek Avia Layout Builder!

It works for me. Hope it can help you!

this is the post i’ve seen:
https://kriesi.at/support/topic/cant-edit-text-in-advanced-layout-editor/#post-119904