There are a few reasons why you might not be able to change your Spotify region. One reason could be that you're trying to change your region to one that's not supported by Spotify. Another reason could be that you have an outstanding balance on your account in your current region. If this is the case, you'll need to clear any outstanding balance before you can change regions. You can check which regions are supported by Spotify here: https://support.spotify.com/us/article/regions-where-spotify-is-available/.