The most common reason for an authentication failure is that an invalid password has been entered. Please open the account properties again and verify that the correct password has been entered.
Verify that the correct e-mail address has been entered.
If Google 2-step verification has been enabled for the account, an application specific password needs to be entered in Gmail Notifier Pro.
For Gmail IMAP accounts it is important to enable IMAP support in Gmail. Read the help section Atom & IMAP to learn more.
It is also important to not configure the Gmail account to disable the IMAP folders that are going to be used in Gmail Notifier Pro.
Check that the setting "Allow less secure apps" is set to Allow in your Gmail settings according to
this Gmail article. This is a new setting that Google enforce in some cases and
introduces issues for many e-mail clients. Please note that the words "less secure" isn't a correct description what this is about, because Gmail Notifier Pro
is compliant with all common security and encryption protocols for e-mail. All major e-mail clients, including Microsoft Outlook, require this Gmail setting to be changed in order to access the Gmail inbox.
First verify that the Internet connection is working properly. If a proxy server is required for Internet access, this must be configured in Gmail Notifier Pro.
It is also important that no firewall software or corporate firewall is blocking the connections to Gmail and the other services used.
Gmail Atom is using HTTPS and is allowed by most firewalls, but Gmail IMAP and SMTP (for sending e-mail) might be blocked.
More information about protocols used can be found in the article
HTTPS and Security
Gmail Notifier Pro is writing log information to the file GmailNotifierPro.log located in your user folder.
The easier way to get access to this file is to open the Options dialog, go to the Administration section
and click the Open button in the Log file section.
On Windows Vista and Windows 7 & 8, the log file can be found in this folder,
where <Windows User Name> refers to the name of your Windows account: C:\Users\<Windows User Name>\AppData\Local\GmailNotifierPro\
On Windows XP, the log file can be found in this folder: C:\Documents and Settings\<Windows User Name>\Local Settings\Application Data\GmailNotifierPro\
Please note that the folder Local Settings can have a localized name on non-english versions of Windows XP.
Faults can be reported to firstname.lastname@example.org.
Questions and faults can also be reported in the forum.