If you have hreflang problems with google webmastertools, and you are using prestashop, take a look here: hreflang module for prestashop. The module is downlodable with a little donation, and it does what it says, it adds the hreflang meta links on your prestashop ecommerce site.
the hreflang links are used by google to handle the content in different languages, the hreflang links tells google that the page you are viewing is the same page also in other languages, Prestashop is multilingual, but it doesn't handle the hreflang links by its own, you need an additional module called hreflang module for prestashop
