I bought Witcher 3 in April 2015, completed the game and haven't played it since. I decided to redownload it to play through it again before buying the new expansion but when I try to download it I am told that the base game is missing and that I don't own it, even though it is showing in my library.

I've attached an image if what i see in the library. What's going on?

Seems horrible. Sent a mail to gog support (look at the help button on top of the site) instead of a post here. It will be more helpful i think. I hope you'll get an answer soon.

Your sole option is to go back to G2Play. They are the ones who sold you a fraudulent product. How can that be GOG's problem?

There seems to be a lot of fraudulent Witcher 3 keys out there being sold. It is best to buy from an authorized dealer - like GOG, so this doesn't happen.

<laugh>

You bought a stolen item and when it gets taken back, you blame the person who had the item stolen in the first place? That's brilliant.

Buy GOG games from GOG. Then they always work. Use shady key resellers? You get what you pay for.

I only wish GOG had emailed me at the time they revoked the key, at least then I would have stood a chance to get a refund from G2play or raise a issue with paypal but now because it is 6 months later I'll lose out, this is why I was a bit pissed with GOG, they should, email any account holder if they touch their account. As for the smartass above, how am I to know G2play would provide a stolen key, I've used them many times without issue so this is news to me. We live and learn.

You raise a valid point. It would make sense for GOG to contact the account holder in this instance.

I would still go back to G2Play even considering the timeframe. It's your only option.

I raised a ticket with G2play after getting a reply from GOG support yesterday afternoon but no response at all from them as of yet.

I'm currently in a similar situation, although my game was gifted to me from a friend as it was a spare code he got 2 free copies when he bought 2 GTX 970s, and my game is now missing from my account...... will see what GoG have to say about that.