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
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We will need a little more information than that to help. Please explain in more detail what it is you are trying to accomplish, and what you have tried so far.
When you register the players choose the team.Can you describe the process of registration that you envision? I understand clubs are a DB join but how to the athletes attach themselves to a particular club for the tournament?
When you register the players choose the team.
My difficulty is like putting a counter so that each team can not be chosen more than 10 times.