This adverb just doesn't fit present tense. This is not a potential sentence. It should be saved for future tense, as in the sentence, "He will work soon." Or perhaps using the verbal noun as in, "He is working soon." Although that last one is more proper using future tense too.
Pronunciation question: I thought the "oib" part was pronounced like the "ib" in "ribbon", but in the recording it's "eye-bríonn"... are both correct or just the latter in the recording?
'go luath' is used for 'shortly' on Irish trains as they are approaching a station. "He works shortly" is therefore on a par with the answer "he works soon". Some the English translations in the Duolingo Irish language section leave a lot to be desired.