Quit my job. HR says they wont pay out PTO due to an amendment to the handbook that I did not sign or agree to, which was not presented until after I asked for my PTO.

Basically the title. I quit, HR is saying “we only pay out where it's legally required to do so.” In my state, it's not required that they pay, but it is required that they honor any agreement that was in place. The handbook I signed says that PTO is paid out upon departure, since it is accrued. They added an addendum now, after I asked when I would receive my PTO check, which they say is dated in 2020 (and was not included in the handbook I signed) which says they only pay out if it's illegal not to. This is wage theft, is it not? Any resources on where I can report it to? It's only 18 hours, but still. It is 18 hours worth of pay that I am technically entitled to.