If I go to browser-based Outlook, I can log in using one of my two MS accounts. Under one email, I have an account at GoDaddy, with IMAP mailbox. Under another email, I have a license for MS 365. If I log in with my GoDaddy account, I don't see the Copilot in Outlook, but if I log in with my email that has a license for MS 365, I see the Copilot icon.
In Outlook for desktop, Product Info shows that it is properly licensed and even shows the Copilot icon among the applications under the license. In this Outlook I have three email accounts configured: the one associated with my GoDaddy account, the one with MS 365 license, and one more (with no MS account). No matter which account I use to write my email, Copilot is not present, even though "Enable Copilot" option is checked. Interestingly enough, I do have the Copilot icon present in MS Word, Excel and PowerPoint. Huh?
I think that having multiple email accounts is what causes this mess. I doubt that it is possible to fix it or even to report this situation: MS is way too big to pay attention to its customers 😒