Android doesn’t allow this automatically, not since A10 or so. You have to manually send to clipboard contents. You should have an option for this in your pull-down menus, or possibly via a persistent notification of you are not on a recent Android version.
You may be able to force it using adb but I am too lazy to bother, since the pull down works quickly for me, and I don’t want my Klipper saved history to fill up too quickly.