You should check the code for the color and size variants if everything is ok. The product https://www.cagnolinofelice.it/prodotto/relax-cuccia-pelosetta-antistress/ is currently working but yesterday I changed a photo and the url was changed and the colors and sizes disappeared. your theme code does not conflict with Woocommerce ?? Also there is an update of Woocommerce and Woocommerce Paypment that I don’t know if I can do given these problems of little compatibility with your theme
I also need to install a plugin for the bundles, do you have a recommended plugin to install with your theme ??