The problem I had was that I didn't see where the mistake was... once I know the mistake pointing it out is pointless.

Feeding back the error you're getting, or the way in which expected behavior is different from observed, can get you pretty far. The bot is fairly graceful at taking feedback. (Your mileage may vary - it works sometimes, but not always. I've also had the bot say "Ah your error was actually <something different than my error>, here is the solution".)

I had an interesting interaction where it said something wrong - I corrected it, and it accepted the correction. I was then curious to what extent it was a pushover - and took back my correction and said that what it originally said was right. It then responded along the lines of "I'm sorry for causing confusion - but <correct statement> is right, and my initial statement was wrong". Pretty impressive!