Cacheing issue?

DNS takes time to propagate. If you have modified the records for a domain the old data may be cached on DNS servers in-between you & the main DNS record (at your router, at your ISP etc).

Try using another DNS server, maybe try Google DNS.

Public DNS | Google Developers

You can check what IP Google DNS is reporting for the site in question…

Google Public DNS

Compare that to the one reported on your Mac, try this in Terminal

nslookup name-of-site.com

The IP should be shown in the output - does that match the new IP?

Another provider is Quad9

Quad 9 | Internet Security and Privacy in a Few Easy Steps

This covers setting a DNS server on your Mac.

http://osxdaily.com/2015/12/05/change-dns-server-settings-mac-os-x/

Eventually the DNS gets propagated & it stops happening.

If you are the controller of the DNS records then consider setting a short TTL (time to live) when updating records. It causes the caches to be cleared faster & can reduce this issue.

P.S. If you are in control of the router you can try rebooting that as it can cache DNS for the local network too.

It seems DNS issue. Try flush the DNS record.

• Step 1: Open the Terminal

  Navigate to Applications -> Utilities -> Terminal

• Step 2: Flush DNS - Type the following command and hit enter.

  Mac OS X Yosemite and later
  sudo killall -HUP mDNSResponder

It is in the developer menu

You get here by going through SAFARI Preferences

Go to advanced and on Bottom tick the box for the menu.

Are you talking about content caching by entering in system preferences > sharing .