Hi there,
From what version you updated your theme? There should be no problem with the update unless it’s coming from very old version or if there are active caches.
We don’t recommend updating any live site as it could always have issues. Updating a core or theme is similar to a redesign or maintenance. And each should be done in a staging copy of your live site. It’s been a practice in web development or software development, updates are provided so users could try it and test it, but it’s not mandatory to be applied on a live site.
I checked your site and yes, tabs aren’t working while the theme is still not updated. Would you mind restoring your site to where it’s still working so we could check? It’s a Woocommerce tab using X shortcode so maybe the issue is already present even before the update.
Your developer is correct, restoring it is much easier and cheaper since this could be related to customization which only applies to the version where it’s created for.
Thanks!