Citizenship

I have question about my friend's case. He filed his N400 base on 5 years green card on December 2015 years. Every processes went smooth untill his biometric fingerprint process. After fingerprint he waited untill June 2017 and in June 2017 he got again second fingerprint notification. He called to USCIS Toll-Free number and talked to second level officer. They told him that after his this second biometric fingerprint process he will get Interview notification and he really got it. He was really glad because after long time he got interview scheduled Yeash he was glad but until his scheduled interview cancelled before 3 days of its time. He called and talked again USCIS Second level officers and this time they told him right your interview time cancelled but purpose is not related to your case. It is something related with Louisville field office.And right now it is more than 1 month his interview cancelled and still he did not get any notification about his case. So guys if have you seen about that is kind of cases which cancelled in last minutes please share with me or if you want you can give advice or something else. I just want to know It is not only my friend happened with him. Thanks a lot!