DNS updates at different times in different places. Sometimes your new address can be seen in some places in only a few hours (or less) while other times it can take up to 72 hours.
While it is updating across the internet, it will sometimes come, and go, and different people will see it in different states, depending upon their ISP’s caching practices, their own system, routers, etc.
As mattail said in his first response to you - if you post your domain name some of us may be able to help you with the research as to what is happening.
It is not at all unusual for it to take a whole day or longer; If you just registered the domain, you will not be able to transfer it to a different registrar immediately (i believe you must wait 90 days), and even if you could, you would just have to repeat this DNS update process again - which result in more down time.
Is you site no longer available on your old server? If you do not cancel your old server until after the updates are complete, you can avoid downtime, as visitors/customers will be sent to one host, or the other, depending upon which DNS record they receive (whether it is updated for them or not).