I wouldn't count out the laser.... on the original wii, it wouldn't play metroid prime 3... because that game used a dual layer dvd, and when it accessed that 2nd layer, the laser was too weak to read it. Some discs are a little thicker than others... a slight variation on it could be making it struggle to read the disc. Discs aren't perfect, and if the laser isn't either, disc read errors happen. I hope I'm wrong but, I'm betting I'm not.

If your wiiu is under warranty, I'd call nintendo and set up a repair. Nip it in the bud now if you can, they usually send you back your original machine, in about 2 weeks, so you won't lose any of your saved game saves and whatnot. Goodluck.

What exactly happens?

Does the disk spin or not? Does the Splatoon logo show up? Is there an error code?

So splatfest is over and I put the disc in today and it worked!!!!!!!!! WOW!!! This is a crazy glitch. Next time I'm going to select sides before the event so this wont happen again. It tells you to select before the event but god damn I didnt think they would lock me out of the game! I must have tried the disc 25-30 times and no go in perfect condition,would play all other games just fine. Finally after splatfest is over it works just fine,I know all online is locked to splatfest but it should still let you play single player. Anyway figured I'd leave an update please tell me if its happen to you.

I went digital for Splatoon. I regret nothing. It starts fast and loads whenever I want it.

I did get a disc error with my Hyrule Warriors game, after summer it stopped working while a few other games played fine. Game apparently fell off my nephew's hand during the summer... but I don't see scratches, etc. I cleaned the disc and polished it and after a few times it worked again.

Haven't tried it since then, but I should check again. 

lol.  So you think the Splatfest causes the glitch? that is really a crazy assumption.