E91 Brake Warning Reset always ticked

[Crumlin01]

Hi. I recently changed my front pads and sensor on my E91. Now before I did this, I will hold my hands up and admit to experimenting with resetting it, which of course didn't work. So I changed them. Now however, I cannot reset the front ones again. The tickbox when you go to reset it is always ticked. I can reset the rear ones happily, just not the front. I thought it might just take some time and miles before it would let me, but I've put 500 miles on now and nothings changed. Any ideas? Have I broke it by playing around? Thanks!