why would an oyster evolve the capacity to suffer and fear and desire to live when they literally don’t control where they move?
there is no proof any nonhuman animal has a “desire to live” because there isn’t proof they understand personal mortality.
as for whether they have the capacity to suffer, which is all that sentience really seems to require, you can’t prove that they don’t have the capacity to suffer because you can’t prove a negative. the best you can say is that you don’t think there is enough evidence to support a claim that they ARE sentient.