can't retrieve messages with Evoution. Server & authentication are correct. Can see messages being counted but none appear.

I was able to retrieve message when I initially set up the pop server for Evolution. I logged out and returned and have not been able to retrieve messages since then. When I click "send / receive" I see the box that says messages are being retrieved but nothing shows up. I know the pop server and password authentication are correct because I'm dual booting Windows and I verified the settings there. Also I have no problem sending messages.