Passive voice

Is there any difference in meaning between these two sentences?:

1. They couldn’t understand him.
2. He couldn’t make himself understood.

In an exercise, I had the uderlined sentence given and I had to finish another beginning with “He couldn’t …” without changing the meaning.
My anwser was: “He couldn’t be understood”. I don’t know if my answer is correct or not because [2] was given as an only possible option. In my opinion [1] doesn’t mean exactly the same as [2]. I feel confused.

Could anyone help me? Thanks a lot.

I agree-- the causative make form is not the same-- it suggests a lot of gesticulating that does not exist in the active original. I like your couldn’t be understood.