3M Engineer interview questions

After a great phone interview with the hiring manager, the HR manager called and left a message asking me to give them some dates when I may be available for an in-person interview. Within hours I replied with my availability. Days went by - weeks - months - and no call back. For a week or so I continued to give them updates on my availability. I even emailed the hiring manager. Neither was professional enough to even send an email saying "we've moved on to other candidates" or "sorry, our hiring process has been delayed, please hang tight and we'll contact you ASAP". I expected more professionalism from 3M.