We do not have workers here. For duolingo the correct translations are:'No tenemos trabajadores aquí' or 'No tenemos trabajadores acá'. The following translation was not correct for duolingo:'Aquí no tenemos trabajadores'. I think the programming part of duolingo is working perfect. However concerning the linguistic, grammatical and other parts of the english, spanish, french and german, they had better consult a professional translator.
There may be mistakes in the lessons. You can submit correct solutions if you think that there is a mistake.
That is an essentially correct translation. I think they probably just forgot to add that permutation of their original answer into the answer bank.