YES

linear polynomial interpretations on natural numbers:

  seven_A = 0
  s_A(x1) = x1
  O_A = 0
  isNat_A(x1) = x1 + 1
  false_A = 2
  true_A = 1
  ack_A(x1,x2) = x2



the condition isNat(ack(seven(),seven())) ->> false() is unsatisfiable for all substitutions.