2006 Ford Explorer won't crank?

Battery and starter both tested fine. Turn the key no headlights or dash lights. Changed out multi function relay under the dash, but still just clicks at relay.

I know this sounds too basic, but often the issue with problems like yours is nothing more that a bad electrical connection. Remove and clean every connection on the positive battery cable from the battery post to the starter. Do the same on the negative cable at the battery post and the end that's attached to the engine block.