Hello,
It seems you have already solved the issue. I check the product page and I see the product page instead of 404.
Please let us know on how to reproduce the problem if it still remains, provide admin rights for the user and confirm the permission for plugins deactivation, and switching to the parent theme. As soon as we complete the testing we will enable all back, however, the site would be without plugins for 15-20 min. You would better make the full backup of your site.
Best Regards