Wishlist functionality

I’ve recently updated our site to 4.8, and also thecartpress, from version 1.3.1 to version 1.5.3.6. Everything seems to work in much the same way, but the wishlist functionality. I’m able to see the wishlist with the widget, I can remove the products from it, but I cannot add any new products to it. I can print the “Add to wishlist” button in the product detail page, but the button does basically nothing. It won’t add the product to the wishlist.

Is this a known issue? Any fixes for this?

Thanks in advance!
Andrés