we left out clean, polish and dry lube the mating surfaces...If it's one of the ones with a plastic ring that turns and adjusts height we've recommended using heat to at least 4 or 5 people that had ones that were stuck and all of them were successful. at getting it to turn. A hair dryer like Stick suggests will work given some time. If you use a heat gun use it on low power so that you don't damage the plastic. If that isn't the problem then a photo would help and you can post one from your own hard drive by using the Go Advanced post option.
you know that most everything is made in China, right?. they just change branding, and a few parts to make a new brand.. unless you find one that says "Made in U.S.A." else they could be "Assembled in U.S.A." from imported parts!..And a soft rubber hammer to coax it along...better yet, buy a new Bosch!