A rejection letter built around the word "original" reads like an accusation of forgery, which is almost never what RDW (the vehicle and licensing authority) means by it. Working out which condition actually failed decides whether there is anything to appeal, because the two possible causes have completely different fixes.
That rejection almost never means your physical card is fake — it usually means RDW doesn't believe you actually lived in the country that issued it. Every exchange-eligible licence comes with a residency condition: you had to hold your normal address there when you got it, not just citizenship or a family connection you used to obtain it faster. RDW cross-checks this, and licences obtained during a short visit home, through a relative's address, or after you'd effectively already moved abroad get flagged as not meeting that requirement — even though the card itself is perfectly genuine. Separately, if you're replacing a lost or stolen licence using an authenticity declaration from the issuing country, that declaration has to be an original, recently dated document; a photocopy or an old one gets bounced too, for an unrelated reason. Either way, ask RDW specifically which condition failed before appealing, since the fix differs depending on which one triggered it.