"ERR_NAME_NOT_RESOLVED": this site can't be reached

Chrome shows this when it cannot turn your domain name into a server address. The site itself may be fine. The name lookup failed.

What to do, in order

1. Check the domain has not expired. Look it up at lookup.icann.org. An expired domain stops resolving within days. Renew it at your registrar.
2. Check the nameservers. The same lookup shows which nameservers the domain uses. They must belong to whoever holds your DNS records (your host, Cloudflare, or the registrar). A wrong pair after a move is the most common cause.
3. Check the A record exists. Run dig +short yourdomain.com or use dnschecker.org. No answer means the record is missing. Add an A record pointing at your host's address.
4. Check www separately. www.yourdomain.com needs its own record, usually a CNAME to the bare domain. Many sites work on one and fail on the other.
5. If only you see it, clear your own DNS cache: restart the router, or run ipconfig /flushdns on Windows. Try the site on mobile data.

If it still fails, send me the address and I will tell you which step is broken.

Want the rest of your site checked after it is back? Run a free 40-point check at tinkeraudit.com.