I am encountering the same problem as posted before. Since updating YOAST yesterday, page builder does not work anymore. I have also updated the Site Origin Widget Bundle, the pages created with page builder still look good but cannot be changed anymore in the backend as no page builder tab is there. There only is a bar underneath the content field with no functions shown.
I have emptied the cache of the caching plugin, but no change.. Please urgently help!
I found the solutions myself – either you upgrade to YOAST 3.0.3 or downgrade to 2.3.5 – then page builder is back to normal again!