ServiceNow Senior Software/Staff Engineer interview questions

Last month I was interviewed by ServiceNow. I had 3 rounds of technical interview back to back ranging from 30 mins to 1.5 hr each. After that I had director round few days later. After everything, it looked like things are on positive side. But after waiting for 3 weeks and repeatedly asking for an update, finally I get an auto generated reply that I am not being considered. Overall interview was good, but the process was disappointing, due to the delay in communicating the feedback that too with no reason mentioned (though that is usual practice). Such experience keep you in the state of wondering what went wrong. I strongly feel that getting rejected after few initial rounds of interview and getting auto generated mail with no reason is still fine. But after all the rounds and after salary negotiation, if company is rejecting, at least should give the reason what ever it be.