It was assumed that her absence may have been caused by controversy surrounding the author's remarks about transgender people.
J.K. Rowling claims that it was her decision not to participate in the January 1 HBO Max Harry Potter reunion. The Fantastic Beasts and Harry Potter author confirmed her absence beyond the archival video in Harry Potter 20th Anniversary: Return to Hogwarts for Graham Norton's Radio Show Podcast.
In a podcast recording, Rowling stated that, contrary to rumours, she was asked to attend the reunion and that no one said: "don't come." The author said that she was invited to be on that, but she decided she didn't want to do it. Rowling correctly believed that it was more about the movies than the books. That was the anniversary's main focus, after all.
Following reports that Rowling wouldn't be attending the retrospective commemorating the release of Harry Potter and the Sorcerer's Stone along with the cast and other members of the creative team, it was assumed that her absence may have been caused by controversy surrounding the author's remarks about transgender people. Several LGBTQ+ advocacy organisations, including GLAAD, the Human Rights Coalition, and The Trevor Project, have denounced the remarks.
Although Rowling had not previously addressed her absence from the show, insiders informed Entertainment Weekly that the author's staff thought the archived comments that were aired during the reunion were adequate. They further disputed that Rowling's choice to skip the event was influenced by her remarks on the trans community.
Several cast members had already discussed the Harry Potter author's public opinions before the reunion, including actors Daniel Radcliffe, Emma Watson, Rupert Grint, and Eddie Redmayne, who all supported the transgender community. Among other actors, Ralph Fiennes and Robbie Coltrane have made remarks endorsing Rowling.
The author was also questioned about her relationships with and conversations with the young cast of the film series, including those who have talked about her. Rowling told Graham that she does, some more than others, but it's always been like that. The author claimed that she was more familiar with a few than others.