Problem on the display of the variants on the product sheets

We have a problem with the display of the variants on the product sheets, when we want to click on another variant (sizes; model; or color) it grays out the add to cart button and therefore makes it impossible to add to the cart, even when returning to the initial variant.

We tried to see through the lines of code in the main-product-liquid section, but unfortunately we didn’t see anything about the source of the problem in question.

The address of the site: https://body-n-you.fr
The password of the site : diepri

Sincerely, the Body-n-you team