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
See Announcement
We are still working on the Joomla update.
If you just need to upload barcode image and not generate it from field data, you could use upload element with image cropping option.You have to crop the image and ensure that there is nothing else then it will work.