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.
If your jump page points to a URL outside of your site then the thanks message is ignored.
Yes, this is what I meant. In this case it's called as an "external" URL (even if this is your-site) and no system message is displayed.My website redirect is with a http://my-site