Question / Problem:
Existing robots no longer are able to access Gmail even when enabling Google's less secure app access. Is there a workaround for this?
Answer / Solution:
Try changing the user agent to use Firefox. For example:
Mozilla/5.0 (Windows NT 10.0; WOW64; rv:70.0) Gecko/20100101 Firefox/70.0
This issue is a result of changes made to Gmail service.
Additional external information: