There's kinda two things going on here. First, the Jellyfin server itself has to refresh the info that it has about files. Jellyfin has an option to automatically scan for new changes, though it will usually take a few seconds after whatever change you made for the automatic process to pick it up.
Second, and more relevantly for your issue. Whatever client you're using has to obtain the new information from the server. In my experience, the web client doesn't like to do this and would prefer to use the data that Jellyfin has already sent. The simplest way to refresh the data is to do a hard refresh in your browser, which for most people can be done by using Ctrl+F5.
Second, and more relevantly for your issue. Whatever client you're using has to obtain the new information from the server. In my experience, the web client doesn't like to do this and would prefer to use the data that Jellyfin has already sent. The simplest way to refresh the data is to do a hard refresh in your browser, which for most people can be done by using Ctrl+F5.