Kudos to customer Natalie for figuring this out. We’ve had a few customers have an issue where the new cap won’t close all the way down. In some cases we’ve sent a new cap that worked better than the first one customers received, perhaps a slight variation in the manufacturing. Natalie however tried the original pin that held the cap in, in place of our replacement pin, and it was just slightly smaller in the middle where it goes through the metal hinge bracket on the kettle, which allowed the cap to close all the way.
So if you have this problem with our new cap, try reusing the original pin, at least for the hole that goes through the metal bracket.