For this kind of issues there are some Troubleshooting steps;
I assume that google DNS is not working!
You can see this post in 2 way:
1-) To learn all troubleshooting steps for any internet connection issues, skip #2 and keep reading the post till the end.
2-)Go to the end of the post, read the bold places. Try it and if it doesn't work turn #1
First of all Im sure that you tried to open another page, probably it is working. Only a specific page is not working.
What you can do is try to send ping to website. Go to Finder > Go>Utilities > Network Utility> Ping: write here the landing page's URL. Send ping. If it is not working, try the next tab LOOK UP. if you can not get any solutions. Don't give up!
Check safari in other user if working, it means you have user specific problem, turn your user and delete all cookies, caches etc.
If other user doesn't work, system related problem is occurred. Shut your mac down. Restart it and press CMD+R during start up. Here we go , you will see Recovery Partition screen. Click on Get Online Support. Try to hit your website. If yes: There is no DNS or IP related problem, your modem works fine, there is a problem in your Software. Turn on your computer, go to system preferences > network (be sure it seems connected)> Location > " + " new one(name is not important probably you will have untitled 2)> Choose previous one and " - " delete it. > Apply changes. refresh safari. Here you go! it solved mine.
please let us know 😉