Hi, on your site, I see a lot of different Javascript errors. E.g. one is redeclaring Phoca Cart variable: VM229:1 Uncaught SyntaxError: Identifier 'phFilterNewUrlSet' has already been declared. It is a part of some debugger:
Usually, this is declared in file: phocafilter.min.js:
so the second declaration in the VM229 debug can break the Javascript. Unfortunately, I don't know nothing about this debug on your site, so this needs to be solved by someone who implemented this debug or uses it.
And hard to say, if this type of error can cause the described problem of there is another issue on the site
Jan