Prestashop Ajax error. Technical error: unable to load form.

A very common problem in different versions of Prestashop (1.5 and 1.6) happens when Ajax running fails in the online store and different errors appear:

· You can not add products to the shopping cart
· You can not change the quantity of items in the order
· We can not delete a product from the order
· An error appears when a user is registering

In all cases, an error appears with this text:

TECHNICAL ERROR: Unable to load form / Unable to change quantity / Unable to delete

All of these errors are related to a problem in Ajax running.

The solution is very simple:

From Backoffice, go to PREFERENCES > SEO + URLs > Turn ON option: Disable Apache’s mod_security module