What a situation
I went through the same.
It was combination of non-synchronized FOB and broken wire inside the drivers door mechanism. The lock barrel was connected to the lock mechanism by "rod" driven by this wire/cable.
Basically, you need the transporder chip from your old key (paired to your immo), which you obviously have.
Then you need to have paired key fob itself to the BCU using the T4.
So if you are not able to lock/unlock door using the key, sounds more like a mechanical issue. I bet the inner cable has snapped or ripped.
You have to get into your car throught the boot - open the middle seat armrest with red button and reach your hand to the left rear door. Hope, you have long arms
The alarm will probably get on
Good luck
