So my dad gave me his Maschine Mk3 and there was the Hardware serial number but because it already got used its not available. I really dont know how I`m gonna use the Maschine now, cause i cant find anything about this issue.
Your dad needs to initiate a license transfer.
Here's a thread containing everything you both need to know:
This is where to contact our registration team: https://bit.ly/NIsupport_RA
I just purchased a Maschine MK3 used from Guitar Center. I tried adding the serial number in NI Access and it says it’s not valid. What can I do to correct the issue?
You can contact support and they will try to contact the owner of the serial, I need to do it myself for my JAM, I just haven't got round to it, and I have never heard of it ever being successful to be honest.