I used a certain domain name temporarily to build a site on. The site has been moved to its own URL and now I want to use the same domain again for another site. I have set up the WP installation but on my computer on any browswer it will not resolve saying the ip is not found. The WP login page resolves on my iPhone using mobile data I have rebooted the WiFi router and also reset the MacBook High Sierra DNS cache but it still will not resolve on the macbook?
Sounds like the updated DNS info hasn't propagated to the DNS server your macbook is using.
If you have access to the DNS's TTL settings, set it to some low number of seconds should speed up propagation before you change the IP it points to.