he would not let me

Present tense is unusual: I try to turn him onto his back but he will not (won't) let me.

I am trying to turn him onto his back, but isn't letting me.

I tried to turn him onto his back, but he would not let me.

GG, could you give a simple reason why the present tense is unusual? As far as I know, we can tell a story in past or present tense. In fact, the original was in past tense and all I did was change it to present tense.

Yes, sometimes we do tell a story using the present tense. It can bring the audience into the story. But overall, we tell stories less often than we simply recount facts.

Fully agree with GG on all counts

Grammar GeekI am trying to turn him onto his back, but isn't letting me.

Have you left out 'he' between but and isn't?

If, in the story, you are talking about a repeated action (still happening) then the present tense is ok.

Example:

He had an accident a couple of months ago, and after 6 weeks he came home from hospital. He has to stay in bed for another 3 months, so I have to look after him. The major problem is that he cannot move in bed and is in danger of getting bed sores. I try to turn him

I was talking something that's completey in the past.

I walk into his room and there he is. I walk over to him and see that he's asleep. I try to turn him onto his back but he won't let me.