Sliding door not opening with remote

[Paulro]

The sliding door has always worked as it should but over the past few days it has become more of a problem to open with the remote and today it refuses to be opened from outside.
So it always needed 2 pushes of the key (normal) and occasionally would fail to open.
I’ve made sure the terminals are clean.
The mechanism works fine with the door open but the key isn’t activating when locked.
We’re in France and plan to be for some time. Anyone got any ideas where to start?

 

[Paulro]

Just to add, the door opens from the inside, manually with a couple of pulls on the handle.