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.
1) go to the label element and change it with: 'FABRIK_LABEL_THIS_IS_MY_LABEL_TEXT'
(SELECT label_table.label from label_table WHERE label_table.fk_field = {thistable}.id AND label_table.language_field = '{lang}'),''
(SELECT library.book from library WHERE library.book = {thistable}.id AND library.language = '{lang}')