It appears that the copyright on the film was not renewed, leaving it in public domain, but the copyright on the story that the film was based on was renewed, w

It appears that the copyright on the film was not renewed, leaving it in public domain, but the copyright on the story that the film was based on was renewed, which became a pivotal point after 1993, when that copyright holder was able to negotiate for licensing for more limited showings. This is covered in the URL you provide, and the details are corroborated by several other sources. It is complicated. One of the effects of the film's popularity in the 1980s is on the popular perception of runs on banks and of bankers - I wonder how much American views of the recent financial crisis are colored by the grim visage of Mr. Potter?