We use the payment processor Authorize.net. The incorrect transaction key was entered, and for about 4 weeks people paid for memberships and registered for meetings on our website. The memberships in Civi show up as "pending", the event registrations show up as "complete", but nothing shows up in Authnet as having gone through... because it hasn't.
I've since fixed the transaction key and did a test run, so I know online transactions work smoothly now. The issue is with the others who paid during the interim... is there a way to put their payments through again now that it's working? Or will these people need to completely re-register?