A4 cabriolet boot won't shut

[MiniMonty]

2003, Audi A4 B6 cabriolet. 2.4 V6 manual.

Hi all,
discovered just now that my boot latch will not operate. Not with the fob or key. The boot just bounces and the latch doesn't move.
Tried oil on the mechanism. Checked that the bar on the body hasn't moved or come loose.
When the boot is closed, turning the key does nothing. Operating the handle does nothing (no sound from the actuator).
Tried slamming it good and hard - no joy.

Could it be as simple as a fuse?
Or needs a new actuator?

All and any advice gratefully received.
Best wishes
Monty