Hello,
Thanks for wp-admin access.
Please provide us with a video of your actions and the problem.
Other pages can be edited without the problem?
Have you enabled the debug mode? If not, provide us with FTP access, so we can do it for you.
One more important test we want to ask you to do:
How does it work when the default WC theme – Storefront is activated on your site?
It is important to check if the problem persists with the default theme to find out if it comes from the theme or from something else. Go to Appearance > Themes > install and activate the Storefront theme.
Widgets could be messed up after switching, so open the Appearance > Widgets tab before switching to be able to move the widgets to the correct area after switching back.
Regards