He had skipped practice Monday and missed multiple practices last week and the final preseason game.
Harden has been seeking a trade since picking up his $35.6 million player option for the 2023-24 season.
The Sixers on Friday said Harden was away from the team because of a personal matter.
Harden has been frustrated for months that his wish to be traded to the LA Clippers has yet to be granted. He arrived late to training camp and continued to practice with the 76ers before missing practices last week.
Harden, who had been tied at the hip with 76ers president of basketball operations Daryl Morey since the latter brought him to the Houston Rockets in a trade with the Oklahoma City Thunder before the 2012-13 season, called Morey a “liar” during a shoe event in China in August.
Harden said on Oct. 13 that there was no chance of that relationship being repaired, and he repeatedly referred to Morey as “the front office” without saying his name.
“No,” Harden said flatly, when asked directly whether he thought things could get patched up with Morey. “This is not even about this situation — this is in life. When you lose trust in someone, it’s like a marriage … you lose trust in someone, you know what I mean? It’s pretty simple.”
Harden has been one of the league’s top players for the past decade, winning three scoring titles and the 2018 league MVP award. He led the league in assists last season.
ESPN’s Tim Bontemps and The Associated Press contributed to this report.