This is a worldwide (but frequently denied) problem with the VWG dry-clutch 7-speed DSG/ S tronic transmission. In an effort to make them maintenance-free they were filled with synthetic fluid on the production line. The problem is that over time and especially in a hot climate, this fluid becomes conductive and fuses the Mechatronics leaving the car with no means of changing gear and thereby no drive. If the car has been fully maintained by a SEAT dealer you may have the basis for a claim against the dealer or against SEAT. There is little point in opening the box and trying to replace the Mechatronics alone. Better a replacement transmission, already filled with mineral rather than synthetic fluid.