On occasion, you may see an error message at the bottom left of one or more of your metrics. If you recently changed the password on that specific data connection, or if the sign-in token has expired, this message will show up. This means that you need to re-authenticate the data source.
Reconnecting is really easy. Click on the Data tab at the top left of the global navigation and you will see a list of the data sources connections on your account. Depending on your permissions level, you might see only those data source connections that you have made or that have been shared with you, or you will see all of the connections made on your account.
Reconnecting an Invalid Auth (Broken Connection)
At the far right of the list of connections, you will see a red box saying "Reconnect" or "Invalid auth." If you click on that you will be prompted to reconnect the data source with the required credentials for that data source.
If you go to the dashboard after reconnecting and still see errors on those metrics, check the datasets that are using that connection. You may need to edit the dataset to refresh the data used.
Reconnecting an Auth Anytime
If you need to change what account is being used for a specific data connection (for instance, if someone leaves your organization and you want to replace the Salesforce account used to another one), you can do that by going to the Data tab at the top left of the global navigation, and clicking on the connection you want to update. Then click on the "Reconnect" button to enter in the new credentials.
To see what is required for a specific data source, visit the full list of data sources or just search the help center.