First you need to first go to the transaction under Securities > Transactions. Once you have located the transaction that is associated with that Certificate you can check Administrative Edit then click Update
Once you do this you will notice in the Certificates tab the certificate involved in this transaction is now marked with a yellow dot. When you open the Certificate you will now notice the fields are unlock for you to change as needed.
Click Update after that you just need to Repair the Certificate on the right-hand side and lastly Validate the Class.