Email not working

Yesterday my email stopped working in outlook on my desktop. I began asking multiple times for incorrect username and password. they were typed in correctly. I then attempted to sign into my email online and had no issues. I have confirmed my third party allow box is checked. Today my email has stopped working on my phone Apple mail app doing the same thing. I have gone in and reset my password on xfinity internet. I can log in on google chrome to the internet application but still can not get outlook or apple mail to work. I have also tried deleting and re adding that accounts on both apps. They will not re add stating incorrect password or username. can someone help me?