Within the Stripe dashboard, you can view all of the transactions submitted through GivingForKindness and their statuses.

Within GivingForKindness, you can also quickly view any transactions submitted via credit card that were not successful.

You can use this information to first check to see if the supporter was subsequently successful, or, if not, follow up with the supporter to arrange an alternative donation method.

How to get there:

Login to your GivingForKindness account.
You'll be on the Campaigns window of the Control Panel.
Choose the campaign's name or the edit link to the right of it.

What to do:

Click on the Reports tab. 

Click on the Credit Card Errors. 

The next page will display a full list of credit card issues.