The Add button grays out after the tribute amount is maxed out. Multiple tributes will need to split out the amount so their separate totals equal the total of the payment.
  1. From the payment select the Tributes tab.
  2. Highlight the tribute and click Edit.
  3. Change the amount to any amount less than the full amount and click save.
  4. Click the Add button to add the other tribute and enter the remaining amount.
  5. Click save.