Is a prestashop server problem, is not our side problem.
They need to solve this, is only their fault, not our side fault.
We have prestashop 1.6.1.3 and module verison it let us download is PrestaShop Checkout v6.3.6.3 and it is bugged also today
Yesterday it was working, and today full day not working
We have report this and there isn't any support, nobody answer in the prestashop support...