Here is a new one for me. I work in higher education and we have many online courses. Currently we have an online course with a Japanese student that can't seem to get Flash Player installed without requiring a credit card. It is necessary for part of her curriculum as the site she need to access requires Adobe Flash Player to be installed. The site she went to download the player was https://get.adobe.com/flashplayer. This is allowing her to install Flash Player but it tells her it will only work for 30 days and requires a credit card. She is running on a newer Japanese MacBook.
I think there is some confusion. Flash Player is free. There is no charge and no trial version available. What the student may be seeing is an optional software offer that displays after Flash Player has been successfully installed. Please ask the student to go to https://helpx.adobe.com/flash-player.html and click the 'Check Now' button. The widget will detect the operating system, browser, and version of Flash Player, if installed and enabled in the browser. If the student is using Safari, depending on the version she has installed, she may have to enable Flash Player in Safari Preferences, see Enable Adobe Flash Player for Safari for assistance.