Using Outlook for iOS in business environments for email and scheduling
Had the same issue when moved from my old laptop to a new one. Tried various things but was unable to get through and was wondering what is actually causing this.
Analysed and found that the new laptop is controlled by a different policy from Microsoft as compared to the old one. These policies are coming into play because of the Domain or other enterprise policies which are controlling our default browsers. The way out is to create a dedicated "Profile" for your account from the default browser, which signs in locally. This is similar to working in Incognito mode where the default Domain or other policies do not really apply.
Myself was using Chrome so created a local Profile and not logging into Google profile. This solved my problem but yes there is a different browser that has to be used now for my Hotmail account.
Hope this help others too!