If you can get to it from your mobile then it’s a DNS issue. You may be caching locally or your DNS server is laggy for some reason.
Try Ctrl-f5 reload on your page in the browser, in this case i don’t think that will help but it could.
What does https://www.whatsmydns.net/
Feel free to post the domain name if you have completed the wp install and we can give you more info.