I recently faced a probably identical issue, and I found out about the cause.
Sometimes, when you add an Actor Component, it might appear in the Component tab, but its actually not added.
To know if you are facing the same issue, do the classic turn off and on unreal editor, re-open the Blueprint, and check if the Actor Component is still present. If it is not, the issue is likely the same.
Just re-add the Actor Component, and it should work fine after.