Does it require some kind of activation-code? If so, can I read it while I scan it on the original scanner?
Not all RFID systems are compatible with NFC. NFC uses an RF frequency of 13.56 MHz (so-called HF), but there are other common RFID systems that use frequencies in the range of 100-150 KHz (so-called LF) or 860-960 MHz (so-called UHF). Your key may belong to an LF or UHF system. Another possibility is that your key is part of an HF system, but uses a command set or an RF modulation scheme that is not compatible with NFC.