Gmail Settings for Messages Import
If the software fails to authenticate your Gmail account.
First, check your email account details are correct like your Email Address and Password.
Second, check if the below settings are enabled for your Gmail account or not.
To import emails into your Gmail account, you need to enable 2 things.
1. Enable IMAP Settings
Activate IMAP in Gmail
To enable importing of emails into Gmail, activate and Enable IMAP in Gmail.
Open Gmail in a web browser.
Select the gear icon at the top right.
Select the Forwarding and POP/IMAP tab.
In the IMAP Access section, select Enable IMAP.
Leave the other settings on the default selections.
Select Save Changes.
2. Enable Less Secure Apps
And make sure Allow less secure apps option is ON