I think GOG is also a bit more reluctant to give a refund like Steam because they have no DRM to enforce policies like steam's.

Yes, there could be some of that. However I would say that I have only, in 3 years, had to contact GOG 2-3 times, once on the release of Witcher Adventure, and they refunded within an hour or so. Part of the problem appears to be them stretching themselves a bit with all that's going on. Its not good I know, but it doesn't seem to happen that often. Steam can give refunds easier as you are only renting it anyways, and like as not you end up on spam message list for doing so.

Little off-topic: That'd be the first to me. Do you have e.g. F310, and it doesn't work with it when you have it in X-Input mode (the knob at the bottom is at "X")? What exactly is the problem, and is it confirmed the same issues don't take place with the XBox 360 pad? Do you mean there is e.g. some driver detection where it refuses to try to work with F310, because it doesn't report itself as a genuine XBox360 gamepad?

I'm just asking because I recall hearing these claims from other games like Darksiders 1-2 and Dark Souls that they really require a genuine XBox360 gamepad, and other gamepads have serious issues, including e.g. Logitech F310. Yet, when I tried them myself, F310 works fine with those games. Maybe people were reporting issues with old DirectInput DualShock-like gamepads, and some believed those issues to be the same for all non XBox360 gamepads, including F310.

So far I haven't found an XInput/Xbox360 gamepad game that wouldn't have worked fine for my F310, but now I am interested to try out whether Grandia 2 would be such, and learn what is the actual issue.

Assassin's Creed and Assassin's Creed 2 required me to add an ini file to play them with my F710, which for some reason didn't work in the vanilla installation. Buttons and triggers behaved as if mapped to different ones. The ini file did fix said problem though, there should be a thread about them in the game forum here.

I'll check that forum then. I only have the first AssCreed (from GOG), I don't quite recall how F310 behaved with it, maybe there was indeed some oddity there..

EDIT: Well, apparently it was the AC gamepad discussion where I already participated last year. :D Can't remember them all...

That reminds me also of Oddworld: Stranger's Wrath. Is it a DirectInput or XInput game? The controls feel somewhat off with F310 in either DirectInput or XInput mode, like the camera rotation etc. At least I got an urge to remap the controls to the F310, after which it felt more natural (I didn't have to use any 3rd party software, just simply remap the controls inside the game). I think this issue was both in the original and the HD version. I wonder if it behaves similarly with the XBox360 gamepad?

What will be the new PC gamepad standard with Windows 10, now that we are in the era of XBone? Is it still the XBox360 gamepad, or the XBoxOne gamepad? I was under impression that the new Xbox gamepad is fully backwards compatible with the old one, but apparently not, as there seemed to be some rather bad issues on Grandia 2 with the XBoxOne (the camera rotating constantly because the two gamepads report Z-axis in a different way with the analog triggers?).

It seems this was not understood by the OP. Maybe the standard response texts could be reworked to better incorporate that store credit is purely optional and a real money refund is also always possible in such cases.

With the referral to the game official support. Instead of saying:

"Uninstall and reinstall the game. If problems persist, contact the developer and nVidia."

maybe that lines should better be something like:

"Uninstalling and reinstalling the game might solve the issue. Unfortunately we cannot offer more actual support. Contacting the developer and nVidia is a possibility to get further help should the problem persist."

Sounds much better and less irritating.

You need to understand that what they told me was - reinstall the game, and if that doesn't work, get help from the developer and/or Nvidia.
No, this was 100% my fault, not GoG's. If I were to repost the email, you'd see how stupid I was in misunderstanding this sentence. Really, it was genuinely my fault. It couldn't have been simpler to understand even if GoG had given it to me in pop-up book format.

In that case there is not much that can be improved (except maybe your reading skills). :)

Nice that you say that here so openly.

Yes, I just want to commend OP for admitting his mistake. Most 'escalation' threads don't end that well and are quite disheartening.
I wish you good (hassle free) fun from now on in here.