Hi.Thank you for your answer.
I switched to Twenty Sixteen theme and problem was still the same.
I found that only when I was trying to open Creator via Appearance>Widgets>
(for example: First sidebar>Layout Builder>Open Creator) it doesn’t work.
When I create new page or I try to edit via Appearance>Personalization>Widgets>First sidebar>Layout Builder>Open Creator – it works (creator opens).
I found a way how to deal with editing but the problem is not completely solved.
Regards