No IMAP access from Android device

Hello, I have previously had IMAP access via 3rd party app (K9mail) setup on my old Android Phone.

When I try setup on my new Nexus 6 I receive an error of "Username or password incorrect" (see attachment)

I have checked all settings and verified them to be correct.

I have also checked that I had enabled IMAP access on the webpage settings.

Please advise....