2nd hand camera

hi I've bought a 2nd hand camera however when I try to link to my account it says the device is already in use, ive contacted the owner I bought it off he has provided me with his log in details which he said he had used for that device and I should be able to remove it, but when I have accessed his account and yes he did give the auth code that gets sent to that email there are no devices listed in his account so I don't know what to do