phone rings different lengths of time before voicemail?

A phone of a friend(both are VZW) rings different lengths of time before reaching voicemail. I gave a test repeatedly in a row(advice from someone else): the first call rang 20s, second call 30s, third call 43s, 30s, 28s, 42s, 28s, 42s. The amounts of time never changes, it never only rings once or twice and it never goes straight to voicemail. At the end of the rings, whichever length of time it takes, the regular voicemail plays. The voice says the number "blah blah" is unavailable, please leave a message after the tone. Just as it always had before this problem started. Could my number be blocked? I know there's no real way to know for sure but just from either experience, knowledge or guess. This person does not use social media so I have no other way to contact them. This is not a person I would expect to block or ignore me. There's no reason at all that I could come up with and they definitely wouldn't without saying so or reason. This number is a number from another state they previously lived in, if that matters. Also, about two weeks ago before this started happening, this same person would call my phone. The line would ring and ring but never reach my voicemail that it set up. I would never get a notification of a missed call and they were never able to leave voicemails for me during those calls. I bought a new phone that has no problem reaching others but am now not receiving calls from this person and am not getting ahold of them. Before testing the repeated calls in a row, I tried calling separate days at separate times but the same problem persists. I cant seem to find any answers. From calls all together, the ring time changes between 20s, 30s, 43s, 28s, 42s and even 1 minute. It reaches voicemail every time. Any thoughts?