Your likely signed a liability release, which protects the barn owner.
well sort of as
in a liability case, you only have to show that the defendant caused your injuries
but in a negligence case, you have to show that the defendant was at fault because he or she acted without due care or breached a duty of care.
In what posted both parties were aware of the issues(s?), as some one posted above then the problem becomes contributory negligence which could be comparative negligence.
Please note, I am not providing legal advise that is what a Real attorney is for, my expernce is from being sued. Just be aware that that laws vary by state or country and most all laws are clear as mud that is why there were 1,327,010 active lawyers as of Jan.1, 2022, use one of those as your source of legal advise
(regarding waivers, a liability release signed by a parent on behalf of a minor child often is unenforceable, varies by state and activity)