If someone blocks you on their cellphone then the cellphone will usually ring just one time and then immediately go to voicemail or just say the person is not accepting calls.
If the cellphone rings multiple times then it usually means that the person who you're calling is just not answering the phone or not near their cellphone.
If the cellphone rings once and then goes to voicemail it might also be because the person has their cellphone in airplane mode or they have the cellphone off.
The battery could have also died in the cellphone and it shut off without the person knowing about it.
If the cellphone rings multiple times and then goes to voicemail it's usually just because the person is not answering or is not able to answer the cellphone.