If you have changed your nameservers to point to our servers but cannot access your website or you receive a DNS error when trying to connect, then this is like down to DNS propagation. Propagation is the time it takes for internet service providers around the world to clear their DNS cache so your new nameservers and DNS information is updated.
There is no set rule on how long this takes as all internet service providers are different and the time it takes them to clear their DNS cache can vary. The general guidance is that it can be from a couple of hours up to 72 hours although the latter is very rare.
As DNS propagation is global, it is normal for people in different locations around the world to see different things. For example, if you have just changed the nameservers, someone in the UK may see the changes before someone in Australia or vice versa.
Note: If you are moving a live website from another host, there is a possibility that during the propagation period you may see the website as still hosted on your previous hosting. It is important therefore, not to make any changes until the propagation has completed as it is possible these changes could be made on the old host.