Conquest Over Time by Michael Shaara audiobook.
Pat Travis, a spacer renowned for his luck, is suddenly quite out of it. His job is to beat his competitors to sign newly-Contacted human races to commercial contracts...
But what can he do when he finds he's on a planet that consults astrology for literally every major decision - and he has arrived on one of the worst-aspected days in history?
Michael Shaara, later to write the Pulitzer-winning novel "The Killer Angels", wrote this story for Fantastic Universe in 1956.