Hi there,
In your case, you might face with an old version of Prestashop, so upgrade your Prestashop could be a good solution. If you are using Prestashop version 1.3, you can upgrade Prestashop from 1.3 to 1.6 or upgrade Prestashop from 1.4 to 1.6 if your Prestashop is version 1.4 and upgrade Prestashop from 1.5 to 1.6 if your current prestashop is version 1.5. Hopefully you will solve your trouble as soon as possible!
Good luck!