Cannot log into Nike.com on iMac

If you have an add-on VPN client app installed, disconnect and remove that and try again.

If not… Seems the particular Nike server (one of many) that you are accessing is overloaded or malfunctioning.

Most major sites have many servers, in various locations around the planet, and sometimes those servers get updated or they can malfunction or have other issues. Many of the providers also use content delivery networks, which can cache results from the canonical Nike website. If the content delivery network can’t connect to Nike, you’ll get errors similar to what is reported.

Put differently… If any of us try this same web-access test, we may well reach a different server at Nike, or a different server within the content delivery network, and we can get a different result.

What to do? Maybe try booting into Safe Mode, as that can clear some odd local problems. If that does not work, try again later.

How to use safe mode on your Mac - Apple Support

Otherwise, wait until Nike sorts this, or contact Nike support directly.

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can examine the report and see if we can determine what might be causing the problem.

Have you installed or run any "cleaning", "optimizing", "speed-up" or anti-virus apps on your Mac?

I'm in the UK and can access www.nike.com/GB, and can switch to the US site www.nike.com

I tried on both Safari 15 and Waterfox ( a version of Firefox), I'm on an M12 24in iMac running MacOS 11.6