To ensure that your donation form is setup to allow sustaining/recurring gifts, follow these steps:
  1. Navigate to Fundraising, Donation Management, Donation Forms tab
  2. Edit the donation form in question
  3. Go to Step 3, Design Donor Screens
  4. Click edit on the Donation Form screen
  5. In the right-hand column, choose "Standard Donation Level" and click "Save Order and Edit Selected"
  6. Scroll down to the donation levels, and on the right, click on "Recurring Behavior"
  7. Ensure that you have the correct Frequency selected for that gift level and click Save
Unfortunately, Support cannot change a single gift into a sustaining gift. You will need to contact the constituent in regards to their gift to have them resubmit or give you the information so that you can setup the recurring gift for them.