You can test your site there to see how easily a visitor can use your page on a mobile device.
Your PrestaShop site probably can not pass that test, which does not mean that your site is not mobile friendly, just because of your site's robots.txt file blocks Google to reach some resources, kind like the test tools is blocked by your site.
Adding several lines to the robots.txt file can fix the problem to allow Google to test your PrestaShop site.
For PrestaShop 1.7 users
For PrestaShop 1.6 users
See this screenshot