"Dit moet niet doorgaan" werd geaccepteerd. But on further consideration, I suspect it should not have been. My Dutch is not good enough, but I think that "Dit moet niet doorgan" means "This must not continue." This is not the same meaning as "This does not have to continue."
"This must not continue" = "It is necessary that this stop."
"This does not have to continue" = "It is possible for this to stop."
Am I missing something in the Dutch?
Does "Dit moet niet doorgaan" = "Dit hoeft niet door te gaan"?
If not, then Duolingo is accepting a translation that it should not.
It is not exactly the same as dit hoeft niet door te gaan, but it is also not necessarily as strong as this must not continue. Though it can be depending on context and how it is said.