Translation:He is not available at the moment.
He is not “accessible" is a perfectly good translation of "tilgængelig." In fact, from a pure linguistic perspective, it is arguably a more accurate word translation than "available." In a wider syntax viewed in the context of the sentence, "available" is a perfectly correct acceptable translation of "tilgængelig." But it is not the only and is arguably slightly inferior to "accessible." Both "accessible" and "available" should be accepted as correct.