Ahh, you don’t actually have any keyframes set on that control. Do you see how the channels are the normal colour (light grey)?
This mean there are no keyframes. Yellow means there is a key on the current frame, green mean it has animation but the current frame is not keyed (and purple means it is driven by a driver)
You are using ‘Available’ but make sure you tell Blender what you want to key beforehand 😉
