
It's the expected behavior if the application is old and designed for IE. Edge and Edge IE mode use different kernels, so it's expected that some applications only work in Edge and some others only work in IE mode. Some old IE specific functions like ActiveX and so on can only work in IE/IE mode.
For mode information about IE mode, you can refer to this doc: https://learn.microsoft.com/en-us/deployedge/edge-ie-mode.
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Regards,
Yu Zhou