Hi @billalkh
Internet Explorer has been deprecated sind June 2022 and has effectively 0% market share. Who ever your stakeholder is, tell him that it is so insignificantly low that no one should care anymore.
Now, to answer your question: this is likely because your website uses modern JavaScript language constructs or frameworks that are not supported and may just render the whole website unusable for Internet Explorer visitors.
Obviously hard to test without an actual browser, but this would be my best guess.
[UPDATE] To put this into perspective, this is from one of my global clients over the last 53 weeks.
Yes, that "browser" is in fact dead!
Personal opinion: any time you spend trying to answer your stakeholder's question is a complete waste!
