Receiving mail from Google via POP / IMAP does not work?

Question

gmail

For the time being, everything worked without problems, but then the receipt of mail stopped working, the message began to display:
[ALERT] Please log in via your web browser: https://support.google.com/mail/accounts/answer/78754 (Failure )
What to do? And why might this happen?
On the Web comes without problems.

Answer 1

It must be allowed to connect from insecure devices.