I think you should restart it! So that you can check if you have a baby it will evolve to a kid...if it did it's probably it's just a glitch but if it still dosen't evolve I'm not really sure but I would get a new tamagotchi if I were you!
Your age counter is probably incorrect. This usually happens because you left it in the 'name' stage too long, so it counted those days as age changes on your tama. Hope I helped!