Thank you both for the replies.
@faisalahammad I was wrong to report the space, in the code it is correct.
@threadi is that the plugin and in fact as you say it is obsolete, I tried to disable it but I lose the link of the pages.
But when I deactivate the plugin I am able to modify the pages and at that point modify them, momentarily I can use this procedure to modify the pages:
– disable plugins
– edit page
– reactivate plugin
I know it is not the best method but we are currently managing the site after the company that has managed it up to now no longer gives us assistance.