Which one is correct ?

Neither.

I never learnt how to use the machine.

Hi and Thanks, can you explain to me why.

I also wanted to know if we use have/has/had in front of a verb, do we MUST have to change the verb into the past participle form, any exception ?

If you are using a perfect tense you must use the past participle.

Learned - is American spelling.

With "never", present perfect tense seems to me the best choice.

I've never learned how to use this machine.

American English doesn't have learnt. If you are speaking to British speakers then use learnt as they will consider learned wrong. However if you are talking to Americans then use learned.

I think if I wasn't sure use learnt, - I think most US speakers will understand you have used the British option where most British will think you don't know the past participle of learn should you

Hi, Dive. Thanks for clarify.
I can't figure it out why this one is wrong, why can't I use simple present in this one ?

I never learn how to use the machine.

Thanks for you help again.

Because you are talking about something in the past. Therefore Dim sum is correct when he suggests that the present perfect is the best as you are talking about something in the past but thinking about the present.

The present would be, I don't know how to use that machine.

Simple present is used for repeated or habitual actions.

They show me this every day and every day I try, but I never learn how to use it. -- This doesn't seem very likely.

It's actually possible to use the simple past.

One summer, back in 1998, I worked at an ice cream shop. We had a machine there for making whipped cream. Every time I tried to use it, I messed it up.

Grammar GeekOne summer, back in 1998, I worked at an ice cream shop. We had a machine there for making whipped cream. Every time I tried to use it, I messed it up. At least once a week, the owner tried to show me how to use it. I was hopeless. I never learned how to use the machine. But I still made great sundaes.

dimsumexpressRight or wrong, I've learned through the years, that "never" is idiomatically associated with perfect tense.

I'd call your interpretation of whatever rule you've heard flat out wrong.
You seem to have misinterpreted the fact that the word 'never' is often used with the present perfect to mean that it is restricted to use with perfect t