Castle on the tailgate is not possible ?!?!

Hello dear Ford driver … I have the following problem … With the Mondeo of my mum the lock of the tailgate has not been working for some time, it can only be opened by the key … clear … says now everyone … is also logical … but usually this also works by pressing the button of the tailgate. And that does not react to it any more. the backgate must always be opened with the key, even if the car is open to itself. vt very, if you always, just to invite a little something or something, the car has to make out. especially since this is not good for the motor!… how can I help my mum there?… can I do something at all or how?… or must mna with it to the workshop? many thanks for your tips … and nice greetings from the Opelforum M!CHA