I've tried to play Pokémon Go lately but I can't select/detect any Pokémon. I see the concentric circles but no Pokémon inside! Any idea?
I've had the same problems. I think it's a server glitch because of all the downloads. It doesn't happen for me now, but when it did, I had to sign myself in again (unusual right?) and then it would say I have absolutely no Pokemon registered in the Pokedex. just wait it out, that's what I did. I probably didn't help, but I hope it did.
If you're seeing the circles where Pokemon are supposed to be, then they have spawned and the game is just being slow to download game assets.
Give the game a good few minutes to load the Pokemon's data in its entirety. If it still refuses to load, it may be worth re-installing the game and hoping that it works better.