top-10-addcount.js.php 404 error

For years I have been using Top 10 without any problems, but suddenly it stopped updating and I saw the following error in console:

jquery.js:4 POST https://www.mysite.com/wp-content/plugins/top-10/includes/top-10-addcount.js.php 404

A couple of days before I had been playing with some other plugins, so I reverted back to the old situation by installing a backup (incl. a db backup), but it did not help, neither did uninstalling and reinstalling Top 10.

Any idea’s?