I am trying to use the wordpress plugin inside of Figma. But when i try to add header of footer i get this warning " Element is not parte of a selected page. Please select the element inside the selected pages."
This means that the Header or Footer are not children of the artboard, or in other words, they are not inside the artboard. You can double check this by inspecting the Layers in the left sidebar.
If you want you can also share the design with me so I can have a deeper look as well.
Let me know if this helps!