MICROSOFT EXCHANGE ISSUES

For the life of me I can't figure out why all of a sudden I cannot add my outlook email to my iphone XR. I've tried logging in via exchange, tells me my user &/or password are wrong. Try through outlook & it crashes. I had it on there previously, why am I now having issues? (it wont login on any of the different year model iphones we have). I can login on my computer & that's about it.