Counterfeit, duplicate, not genuine, copy, etc.
The fakes these days are really good--to the point they may even function well for a while. But if not genuine, they will fail faster or not have all the features (in the case of network cards this is usually the tell-tale sign).
Ways to avoid this is to only buy used from reputable recyclers if they are older parts, buy new only from reputable online retailers, preferably with a physical retail store as they won't be able to get away with selling fakes too long before people come to their location mad as a hornet.