the solonoid is a know issue. it was be actuating, but will only be going 80% of the way.
I remember this happening to mine, - some people said you could bang on the
badge when its at 90 degrees, but i can't fathom why that would work, but give it a go..
you need to pull off the trim inside the boot to get at it, i put some silicon grease on mine and it worked for another 9 months or so, after that i did that again but left the trim off, (as to remove it you need the boot open). and never had another issue with it..
typical.
you 'should be able to get in the boot via the rear seats, then pull the trim away - grab with both hands, one either side of centre at the bottom of the window and pull, need to be brave, then you should get just about enough access to get a hand down there, pull at the metal arm, IIRC it works on a pivot where the solenoid is horizontal and its connected via a pivot vertically to the lock.
thread here: sadly the photos no longer show.
https://forums.seatcupra.net/index.php?threads/boot-not-locking-heres-how-to-fix-it.135787/