Outlook not receiving email from my yahoo email account

This is the third time in a year Outlook arbitrarily stops retrieving/receiving emails from one of my yahoo accounts. The previous two times I was unable to get it to work and Microsoft tech people also had a difficult time getting it to work, but they eventually were able to. Do you know why this keeps happening? And why I can't get it to work again when it does happen? And, most importantly, how I'/we can get it to work?