A senior user may petition the United States Patent and Trademark Office to cancel a registration on the basis of prior use pursuant to Section 14 of the Trademark Act, 15 U.S.C. § 1064. In a cancellation proceeding, to establish priority on a likelihood of confusion claim brought under Section 2(d) of the Trademark Act, a senior user must prove that, that it owns a trademark previously used in the United States and not abandoned.”