You will need to replace the old S-Control button with new VisualForce Page that had replaced it. You can do that by doing the following: 
 
  1. Go to a Donation Record Page and click Edit Layout in the top right of the screen. 
  2. Find the button under Matching Gift that says "DEPRECATED DOnation Matching Gift Create Button") and remove it by hovering over it and clicking the Remove symbol. 
  3. On the Layout Properties panel at the top of the page, select Visualforce Pages. 
  4. Drag the Donation_Matching_Gift_Create_Button onto the layout where the old button was. 
  5. Click Save.