The rapper was scheduled to perform for a second night in a row Saturday at PNC Arena in Raleigh, NC ... where he'd just played a massive concert the night prior as part of his North America "Utopia Circus Maximus Tour" -- which has gotten rave reviews so far. Before Friday, Trav had already performed in Charlotte, NC ... so this woulda been concert #3.

Unfortunately for his fans wanting to catch him for the back-to-back ... they were out of luck, receiving news just hours before the start of the gig that Travis wouldn't be taking the stage.

A message went out to all ticket holders for the second PNC show, which reflected what was posted on the door to the actual venue -- reading, "Tonight's Travis Scott concert at PNC Arena has been postponed. Fans are encouraged to hold on to their tickets as they will be honored for the TBD new date. We apologize for any inconvenience. Thank you!"

That didn't sit well with a lot of people who'd flocked to the area -- in some cases, from far away -- to catch him live ... and some folks posted their disappointed reactions online.

WRAL News also interviewed a handful of would-be concert-goers ... who said they were given no explanation whatsoever for the postponement -- not from the third party vendor, the venue or from Travis/his team either. What seems to sting here is the fact that he was literally there on Friday ... and nothing seemed amiss. If anything, it looked like a rager.

Of course, the irony here is that Live Nation added this second Raleigh show in response to an apparent demand that presented itself way back in early September. His first concert there in town had sold out, so they threw in another -- where tickets also flew off the shelf.

It goes without saying, Trav needs this tour to go well ... it's his firs time on the road here in the States since the Astroworld tragedy -- and he could use all the good will he can get.