If you changed your Google email "2-Step Verification" settings or the "Less secure apps" settings, Google says "These changes may take up to 24 hours to propagate to all users."
If you have (2SV) 2-Step Verification with Google, you will need to create an "App Password" if you're using your email's SMTP settings your website. Go here for more details:
https://support.google.com/accounts/answer/185833?hl=en
We recommend 2-Step Verification because it adds an extra layer of security to help keep your email account secure. Most people only have one layer – their password – to protect their account. With 2-Step Verification, if a bad guy hacks through your password layer, he'll still need your phone or Security Key to get into your account.
For trusted devices/apps such as your website, you can create an app password. An app password allows you to change your email password whenever you want and you don't have to adjust your website's email integration because your app password is independent of your email password.
If there are other devices/apps that you trust with logging into your email account (such as your computer or other phones, tablets, etc.) that you don't want to have to adjust for password changes, or receive the 2-step verification code, you can create app passwords from them, too. To do this, login to your Google account, then go to:
https://myaccount.google.com/apppasswords
To learn more about Google's 2-Step Verification, visit: