Recently, some Websites won't load unless VPN is turned on

If it's multiple devices then it does point to something at the network level, not device level. The first culprit would be your router, then your ISP.

Your router may be misconfigured, handing invalid DNS, or blocking/mis-routing traffic to certain IP addresses.

Some 'smart' routers also do content filtering, and this may be getting triggered by something on the sites in question.

I know my ISP-provided router does this. Generally it works well, but the blacklisting system is opaque, at best.

If it's not your router then it could be your ISP. They can also have misconfigured configuration, router setup and content filtering, but it's even more opaque and harder to diagnose.

The problem could also be IPv6 vs. IPv4. Your Mac will try to use IPv6 where possible, but the router/ISP may not support that.

The reason the VPN circumvents it is that your request is encrypted and sent over the VPN, where the VPN server decrypts it and establishes the connection to the end server. To your router and ISP, it just looks like another connection to a semi-random server, so their misconfiguration/blocks don't kick in.

For troubleshooting, I'd start by going offsite - if the same device (sans VPN) can connect to those sites while on cell service or at the local coffee shop, then it's not the device.

Net turn off IPv6 (if it's on), and try again.

Next would be DNS - the ISP's DNS server may be blocking the connection, so change the DNS servers you use (via System preferences -> Network). Override whatever your router/ISP set and use Google DNS:

8.8.8.8

8.8.4.4

If it still doesn't work, open Terminal.app and try:

traceroute support.apple.com

You should see the path between your device and the server support.apple.com

While not definitive (some routers will not respond to traceroute), it might provide some insight.

(for grins, you can run the above while the VPN is on and off to compare the difference, and learn how much the overhead the VPN is adding).

Hopefully that will give some insight. You can also post back the actual message from Safari which can give hints as to the problem (e.g. can't find server, connection refused, SSL mismatch, etc.). These error messages aren't always easy to decode, but someone here might wean something from it.

Possibly, but requiring a commercial VPN is just not normal. Usually, it's the other way around. Try uninstalling the "Nord VPN" product in accordance with its instructions.

It is not sufficient to merely disable it. It must be completely uninstalled followed by reverting all network settings to their default conditions.

Well, that's interesting.

If I read that right, your request is being sent to Akamai in South America (assuming 'baires1.bai' points to Beunos Aires, Argentina, but that could be wrong). Assuming you're in the northeastern US, that seems like the wrong place to go.

It does look like a DNS issue, though. The DNS resolves the hostname to that 2.19.36.146 address, which is in Akamai's network, which is likely valid. But there's no reason for the DNS resolver to send you there.

What are your current DNS settings? Does the routing change if you change the DNS server as described in my earlier post?

It appears that "Nord VPN" did something to alter that Mac's network settings. Did you remove it as I suggested? Merely disabling such things is generally inadequate. It has to be removed and any network settings it altered need to be reverted.

Try creating a new network location according to Use network locations on Mac - Apple Support.

I have no idea, but VPNs are not necessary, convey zero benefits, generally cause problems, and are extremely popular for reasons that escape my understanding. Most connection problems are solved by removing them and all similarly categorized junk — broadly defined as things that prevent Macs from working the way Apple designed them to work.

Is an extension or something loaded during my computer startup that could cause the problem I'm having.

Quite possibly.

Also, I'm having this problem on at least 5 different devices - a mix of MacOS and iOS devices.

If they are not similarly affected then you may have effectively isolated the problem to beyond your Mac. Investigate your router, wireless access points, and if you have the opportunity to use a different wireless network or a different ISP, try that also. In the meantime please review If Safari doesn't open a page or work as expected on your Mac. There are many useful suggestions in that document, among some that are less than useful, but exhaust all of them. If you need more help by all means please write back.

That helps.

It indicates DNS is returning an IP address (it could be the wrong address, but at least we have an address).

It also indicates that you can connect to the server (so not, necessarily, a routing issue).

You're not getting a reply back, though, which could be a routing issue, or filter.

Let's see what the rest of the testing comes back with.

That's what I would do.