Sometimes Steam gives you an error, but has actually put Thimbleweed Park in your library. Restart steam and look in your library.
In most cases we've heard of it's because Steam isn't fully updated. It might be silently updating in the background. The easiest fix is to wait for it to update, or in some cases uninstall the Steam client and then reinstall it.
There is a step in the GOG's Mac installation where it opens up a finder window and needs you to click on which directory to install to. It's not well labeled and other users have reported that it doesn't make sense.
GOG have asked us to direct anyone having issues with the GOG installation of Thimbleweed Park to go to their Support Center. Then click the "Sign In" button in the upper right-hand corner, then select "Game Technical Issues", find Thimbleweed Park.
If you're a backer and would like a GOG key, you need to sign up using this form.
We are also working on iOS and Android and they will be out in a few months. We will consider other platforms, but we have no firm plans currently. We will announce when we know for sure.
Please email firstname.lastname@example.org with details about how you plan to use the review copy and we will consider your request. Due to a high volume of requests we can't respond to all emails.
~/Library/Application Support/Terrible Toybox/Thimbleweed Park
AppData\Roaming\Terrible Toybox\Thimbleweed Park
~/.local/share/Terrible Toybox/Thimbleweed Park
Mac App Store:
~Library/Containers/com.terribletoybox.thimbleweedpark/Data/Library/Application Support/Terrible Toybox/Thimbleweed Park
If you're still having trouble with Thimbleweed Park, please email email@example.com