TIP: in my case the inner part of the boot lock was nlocking a piece of the plastic ring. So after trying for half an hour I figured out to losen the two screws of the lock. Remove the plastic cover to losen the lock and it will give you just a little bit more room to position the inner ring and lock it.
This is what I found out after faffing around so I you tubed it and here I am reading your comment. How do you remove the plastic cover on the lock. Does it just pop off? Don’t want to to break it