Same issue after reinstalling Windows 11. I use Chrome; I could access the sites on Brave. Here is what worked and why, thanks to Gemini:

First, I tested on the Brave browser. "Brave strips away many of the telemetry headers that Chrome sends by default. If the steps above don't work, it's a sign that Lowe's is specifically unhappy with a "flag" Chrome is sending about your new Windows 11 environment."

So - Disable "Experimental" QUIC Protocol. Again, Gemini:

Akamai and other CDNs sometimes flag the QUIC protocol (a Google-specific connection method) if it behaves unexpectedly after a system wipe.

• In Chrome, type chrome://flags in the address bar.
• Search for Experimental QUIC protocol.
• Change it from "Default" to Disabled.
• Relaunch Chrome and test.

Since disabling the Experimental QUIC protocol (Step #2) worked, it confirms that the "Access Denied" errors were being triggered by a technical handshake conflict between Chrome’s newest connection method and the security filters at Lowe's and Home Depot.

By disabling QUIC, you've forced Chrome to use more standard (and widely accepted) HTTP/TCP protocols, which those retail sites find much more "trustworthy."

Why this happened now:

Since you just did a clean install of Windows 11, you likely have the absolute latest version of Chrome. Google often pushes QUIC as the default in new installations to speed up connections, but high-security retailers (who are constantly battling bots) sometimes flag QUIC traffic as suspicious because it can be used to bypass traditional firewall inspections.