Hi @Sam Teddy ,
According to your description, I want to know if the new page opened by window.open() is also in Edge IE mode? This may be the cause of the problem, because Edge IE mode pages are actually running IE tabs, and if the new page running in Edge instead of IE mode, by default Microsoft Edge and Internet Explorer processes do not share session cookies. Simple refer to this doc: Cookie sharing from Microsoft Edge to Internet Explorer.
In this case, you can try adding the new page to the IE mode sitelist as well, which should solve your problem.
Best regards,
Xudong Peng
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