Two of the most used excuses I hear from sellers for non-functional articles are ‘It worked here without any problems’ and ‘It must be damaged by the postal service’. In rare occasions this might be true, but most times these are just stupid lies. Here is a good example …
In the following pictures you see a european Super Nintendo console. Unfortunately it didn’t worked - although the seller stated in his auction description that it is fully functional - and so I opened it, to reuse the case which was still good in shape.

After I opened it, it was clear why it didn’t worked: An ugly, brown and dried fluid covered parts of the board. It looked like the seller filled it with a very common and well known soft drink and afterwards cleaned the case. Of course I had to ask, why it didn’t worked without telling him, that I opened it. The answer - you can already imagine it - was: “It worked here without any problems, probably the postal service damaged it”. Sure - someone from postal service opened the parcel, opened the SNES, filled it with a softdrink, waited until it dried and repacked the parcel …