Fix C# Chrome Session Issue

I have a C# .NET executable that launches Chrome to visit a static, cookie-based URL. When I open the page manually—15 separate Chrome profiles, then close all but one—the remaining window stays logged in just fine.
The moment my EXE opens a second browser window, however, the site throws a “session expired” error, even though the URL and credentials are identical.

I need someone to dive into the code, find out what I’m doing wrong with session handling, and deliver a clean fix. You may discover that the problem lies in the way I spawn Chrome, share user-data directories, or pass command-line flags; whichever it is, I want to understand it and see a working solution.

Deliverables
• Code review with a concise explanation of the root cause.
• Updated C# source that lets me open many parallel Chrome windows without killing existing sessions.
• Step-by-step setup notes so I can reproduce your results on Windows 10, .NET Framework 4.8, latest Chrome.

If Selenium, PuppeteerSharp, or a different launch method solves the issue, feel free to integrate it—clarity and reliability are what matter most.