Hello there,
Have you Configured IE mode policies? You can try to configure the policies first and then try to import the certificates .
You can configure Internet Explorer to open directly within Microsoft Edge (IE mode). You can also configure Internet Explorer to open with a standalone Internet Explorer 11 window. Most users prefer when sites open directly within Microsoft Edge in IE mode.
Configure IE mode policies https://learn.microsoft.com/en-us/deployedge/edge-ie-mode-policies
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