PopMan

I have been trying to use PopMan as a simple email client. It seems to work fine for 2 email accounts but not for a third. The account details are identical to those that work in another client. But with PopMan an attempt to update the account yields no response, No error message. Nothing. Does anyone have any suggestion of what might be wrong or what I might try to figure out the problem? I have tried increasing the time out to no effect. I have no other ideas.