My Wordpress Site Health Status check showed me some critical issues that I needed to take further look at. "The REST API request failed due to an error."
Error: cURL error 28: Operation timed out after 10000 milliseconds
with 0 bytes received (http_request_failed)
After a lot of search results that did NOT lead me to the right direction I finally stumbled up on a short article about this subject. A few items in a list on "How to Fix" this. The most interesting line in the article mentioned the Query Monitor plugin to check the status of the HTTP API Calls in the admin page where the error is displayed. And that vas the single most helpful plugin I ever found. Within a minute I had identified the problem the problem which was I my case the WP Social Avatar plugin.
This Query Monitor plugin saved my day, but mostly a lot of time.
*** EDIT *** It turned out I had second plugin causing the same error. "PHP Code For Posts" that has has been closed and is no longer available for download.
--cheers