I don't know the history of the site, so I can't say how it arrived at its current state.
What I can see, looking at the source code for the page, is that the second View, giving the View not found message, was a View created with the block editor, with ID 299562, and with a preview with ID 299563. Block-based Views have two associated posts, if either is missing the View cannot be edited. In your case, checking wp_posts there are no posts with those IDs, they have been deleted.
At the top of the page there is another View, with ID 300848, although that appears not to be a View created with a View block directly on this page. In any case, checking wp_posts there is also no such post with that ID.
I don't know how they were deleted, but you can't edit the Views because they don't exist anymore.