Theme issue after upgrading to WP 5.5

Good morning,
after upgrading to WP 5.5 some sites using the (modified) Atahualpa Theme have encountered a very unusual problem: Options rel links no longer open links to their respective pages.
It seems that the event of the script that operated to open the related pages has been removed from the action of links.
Any ideas on how to fix this ugly mess?
Thank you!

The following is the script:

function() {
  var newTab = $(this).attr('rel');
  $("div.tabcontent").css("display", "none");
  $("div#" + newTab).css("display", "block");
  $("ul#bfaoptiontabs li a").removeClass("selected");
  $(this).addClass("selected");
  document.cookie = 'atahualpatabposition=' + newTab + ';path=/';
}