This article explains how to reset your ProBackup password, whether you are signed in or signed out.
When signed in
Go to Settings > Profile.
Next to Password, click the Edit icon.
Enter the verification code sent to your email.
Enter your new password and confirm.
When signed out
On the sign-in page, click "Forgot password?".
Enter your email address and click "Send me the link".
Follow the instructions in the email to set a new password.