Try the following:
- Make sure that you are using the correct environment: https://ca-test.adyen.com or https://ca-live.adyen.com
- Check that you filled in your company account name under Account, then your personal credentials.
- Check that your credentials are not being incorrectly pre-filled by your browser.
If that doesn't work, click Forgot your password? or contact your admin user. If you are the admin user, contact Support.