If you use 2-Step-Verification and are seeing a “password incorrect” error when trying to access your Google Account, an App password may solve the problem. An App Password is a 16-digit passcode that gives an app or device restricted access to your Google Account without having to divulge your personal password and complete access to your Google Account.
1. Add an App Password
Note: Google now requires that you have 2-Step-Verification enabled before you can set up an application password.
Visit your App passwords page. You may be asked to sign in to your Google Account.
In the Select app dropdown menu, choose the app you’re using. You can also select Other and enter you own custom app name.
In the Select device dropdown menu, choose the device you’re using. You can also select Other and enter you own custom device name.
Click Generate.
In the Generated app password modal, copy your 16-digit password and paste it into your application.
Select Done.
After you’ve clicked done, you won’t see that App password code again. If you ever lose your app password, you can just generate a new one following the above steps.
You should now see a list of apps and devices you’ve created App passwords for.
2. Allow access to your Google Account
As a security precaution, Google may require you to complete an additional step when signing into a new device or application using an application password.
Visit the Display Unlock Captcha page and click Continue.
Complete the CAPTCHA if you are prompted.
If your account was unblocked, you should see a message Account Access Enabled.
Source: https://devanswers.co/create-application-specific-password-gmail/