It's called the synthetic form of the verb, and is used in primarily in Munster. Both should be accepted.
If you know that your translation is correct but isn't marked as such, I would use "report error"->"my answer should be accepted". Sadly you will normaly NOT receive a reply if your translation wasn't accepted, only if it was.
So far it mostly has been--there have been one or two times when "madadh" and "girseach" have been marked wrong, but I guess why this is beta. If your correct Donegal answer is marked wrong, let Duolingo know--it seems that, although they teach the CO, they accept all correct forms.