Good afternoon, Rebecca. If when you created the credit, you entered the original invoice's number in the credit's "Ref #" field, then the two documents should link together. This may be able to be done even now. Having done that, Sage may be able to "locate" the ledger transaction. 

If that doesn't work, then did you try to void the credit (3-2 screen, Edit, Void Invoice)?

This is what it is not allowing me to do.  The status is set as paid so I'm not sure if that is the issue.  If it is I am not sure how to change the status.

Yes, if marked paid, then you must delete the payment first.

Except there is no payment it's a credit entry linked to an invoice.

Except there is no payment it's a credit entry linked to an invoice.

If the credit was applied via cash receipts you can void the cash receipt entry first , then fix the invoice then redo cash receipt.  In the 3-2 window if the go to transaction is greyed out then that entry was enter as a paid status and cannot be edited or voided because its has no gl record. If entered as paid and no gl record then the account # does not matter anyway.  
if the credit was applied automatically using the reference field you cannot void or alter which is why I dont recommend applying credits that way. 
you may have to make new entries to correct the entry or just make a note and post a JE to fix it

This is exactly what we did.  Thank you so much for your help.  I will have to look into a better way to apply these credits so that we can get them to hit the jobs correctly.