iPhone X 256 GB storage/download capacity

I am downloading videos within an app. After downloading a few it now tells me I need to free up space to be able to download any more. Upon going to Settings > General > iPhone Storage - it says I have 19.6 GB of 256 GB used - leaving me over 230 GB of space. Why won't it let me download any more videos within the app if I have that much storage space free?