Credentials for all providers will be saved when you create an account for the first time. All credentials are securely stored in a vault. You can update or delete credentials by clicking the fourth option in the dropdown menu.
If your most recent crawl failed, it could be related to your credentials being no longer valid. You'll need to update the credentials for the account. That will renable the daily scanning of your account.
This is how an Account looks when credentials are invalid:
Click on the red key, and delete and upload new credentials. In this example, the following ARN for the AWS Account was no longer valid: