For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
but this is not an error message. It is only the line number which it appears. What error message you mean?... i got this error message in adding validation "/administrator/components/com_fabrik/models/plugin.php on line 40" . Could anyone help me?