Question: no serial number!
So I bought a 2009 MacBook refurbished off ebay for change really, and everything works great. I needed some help from apple for something so I went to go chat online and it asked for my serial number... it says "unavailable" in the about this Mac section and under reports' and theres no serial number printed on the bottom of the laptop itself either ! help!
MacBook, macOS High Sierra (10.13.3)