Gmail error 78754 is a password confirming error which comes when you try to log in to your Gmail account and it will show you a message that your username or password is incorrect. This error generates while Google detects your account is suspicious or there is any kind of security issue related to your account.
You are not able to sign into your Gmail Account and might be seeing any of the following messages while attempting to sign in:
1. Username and password not accepted
2. Invalid credentials
3. You are asked to enter your username and password over and over
The following could be the possible causes behind this error to appear:
1. Gmail is not recognizing your password.
2. You are signing in from a new location or device.
3. You might be using invalid credentials.
4. You didn’t use 2-step verification which generates another app password.
5. Google detects your login as suspicious.
You can try any or all of the below-given solutions to fix this issue:
1. Check if you are entering the correct password while signing in.
2. Update the email client to the latest version in case it is not updated.
3. If you have enabled 2-step verification, then sign in with an app password.
4. If you do not use 2-step verification, then you can allow less secure apps to access your account.Select the “Enable” option next to “Access for less secure apps”.
5. If you have changed your Gmail account’s password recently, you might be required to enter your Gmail account information again or repeat the complete Gmail account setup on your other email client.