This is due to the behavior of a web browser's auto-complete or auto-fill settings feature. That feature fills in the donor's name to the Tribute name fields, but it does not select the Tribute Type field.

When this message occurs, remove data from the Tribute section fields or turn off the auto-complete or auto-fill in the web browser.

(Tip: Consider a separate page and donation form for Tributes. This will let you customize the page, form, and form email acknowledgement just for these gifts. Don't forget to add a link to your main giving page/form to the Tribute gifts page.)