I found that my problem was with an add-on for Elementor, a 3rd-party plug-in called Elementor for Devices. Elementor and Elementor Pro had upgraded and were no longer generating a variable that Elementor for Devices required. I had to disable Elementor for Devices and then I could edit the page again.
Check your debugging console for errors and track them down. The issue isn’t likely with Elementor or Elementor Pro but rather some other free plugin made a year or more ago that hasn’t been updated to be used with current versions of Elementor.
I hope this helps.
