can send but not receive emails

Had to change my ISP password which I did. I then removed all passwords from Thunderbird. I then downloaded the newest version (listed below) After the download I clicked on get messages - no response - did not ask for a password. My ISP pop address is properly listed. I went further and clicked on write - a box opened up asking for a password. Of course I entered my new ISP password and it showed up under saved passwords (smtp etc). I can write and send messages but not receive. I would appreciate a fix to be able to download messages - I miss my Thunderbird. Thank you - I must admit I'm not very teck savvy