Let panexperientialism be the view that all fundamental particles have fundamental experiential or protoexperiential properties.
There is good reason to doubt this. Fundamental particles differ as to whether they have fundamental properties like mass, charge and spin. Thus, we should expect them to differ as to whether they have experiential or protoexperiential properties, and hence we should not expect all fundamental particles to have such properties.
A variant argument. For any subset S of types of fundamental particles, there is S-experientialism, which holds that all and only the fundamental particles from S have the fundamental experiential or protoexperiential properties. Panexperientialism then is S-experientialism where S contains all fundamental particle types. But there are many values of S for which S-experientialism explains our consciousness as well (or as badly) as panexperientialism—for instance, S might be all fermions, or all leptons. So what reason do we have to think that of all these, panexperientialism is true? Well, we might think it's the simplest version. Yes, but the simplicity argument is defeated by the inductive considerations of the previous paragraph.