"Oh, you may have 6 years of experience with IT support, using various different ticketing systems, worked in environments using all the major operating systems, and have done some system and network administrative work, as well as multiple certifications indicating that you know everything we're looking for and then some, but you've never worked with the ticketing system that we use? OK, bye! You're useless to us! Your resume is going on the bottom of the pile!"

That's like throwing away an application because they didn't use the same ticketing system is like refusing to hire a highly-experienced pilot because the seats on the planes they've flown aren't the same model as the plane the airline flies.