While there is some controversy whether you only take a step or you can also make a step, I think the "The child made one more step" should be accepted.
I'm afraid "... made one more step" doesn't collocate in English it needs to be "take a step". We do have "make a move" but that wouldn't express the same idea.
I tried, "The child takes another step." and it was marked wrong. Thoughts?
he/she/it takes (simple present) = κάνει, he/she/it took (simple past) = έκανε.
Edit 20-May-2017: Please note that the standard translation for take is παίρνω in Greek, and κάνω=do, butno one 'does a step' in EN or 'παίρνει ένα βήμα' in GR.
"The child did one more step" - should this be correct also? It sounds odd in English but I always think of the verb as made or did.
In English, the expression is "take a step". Translating word for word is not always beneficial.