Like many of the services you use (e.g. Xbox) Hiri does not allow you to enter a two factor authentication code when logging in to Outlook.com. But there is a work around. Basically, you need to create an app specific password. You can do this in your Microsoft security dashboard.
1. Log in to your Microsoft account by clicking on your profile picture in Outlook.com (1) and choosing View Account (2):
2. Click on Security
3. Choose More security options at the bottom of the page:
4. Scroll down to the App Passwords section and choose Create a new app password:
5. Copy the app password. This is not the password you will use with Hiri. That's it! You should now be able to use your Outlook.com account with Hiri.
6. If it doesn't work, simple generate a new password and try that by clicking on the Create another app password link and trying that password instead:
