The 20-year-old Brazilian spent 2017-18 with the Catalan club, making 15 league appearances but only starting once, after joining City from Vasco da Gama.
He impressed Pep Guardiola during pre-season, with the City boss keen to include Douglas Luiz in his first-team plans followed the failed attempt to bring in Jorginho from Napoli.
However, the youngster was denied a work permit leaving Guardiola frustrated with the process ahead of the English transfer deadline.
"We'll try to help him go on loan again and get the work permit," Guardiola said at an August 10 news conference.
"It's difficult for me to understand, one guy who doesn't see him in training has to judge. He has the quality and ability but I accept the rules, even though I don't understand it.
"The Brazil manager [Tite] and myself know more but it is what it is. I am sad and disappointed as he could play with us, and the reason why we spent so much to buy him is he has a huge capacity to play with us, we work a lot with the work permit as we believe he can play.
"We decided to play him [in pre-season] as we believe in him, but they didn't know him, no one game or training session. I don't understand but I'm in England and I can accept it."
As a result, Luiz will now continue his development in La Liga – hoping for more opportunities to impress under Girona boss Eusebio Sacristan than he enjoyed under predecessor Pablo Machin.