Well, if you just realized that your brain wasn't working properly, then yes. Your translation seems a perfect fit.

If it's been the case for a while now, then it's better to say:

мозги не работают - мозг не работает. And a bit of a idiomatic expression for you:

Голова (башка) не варит

Also you can replace мозги with голова or башка (a bit rude) in all examples above.