Like Fazerider said, if You did not remove the part in the middle - garage must have lost the ball. I had same problem after fitting new plates and EBC springs. Could not figure it out for ages. In the end went back to old springs (actually to 6 long ones off Thundercat - they are identical - loong story 
... and it worked. It seems to me that heavy duty EBC springs are too stiff.
... and it worked. It seems to me that heavy duty EBC springs are too stiff.