I'm really at a loss for words here. I've spent about 8 hours of my own time trying to get this resolved, spoken to numerous people at Matrix and Slitherine, and spoken to support, and everyone's fobbed me off with "go to support", at which point support have been unapologetically useless.
I'm going to summarise for the sake of convenience as well as getting any obvious questions out the way: I bought Distant Worlds: Universe (DRM-Free) a while ago and had no issues whatsoever playing it - I've recently formatted and upgraded to Windows 10, and the other night I decided it was time to grab my Steam key. I logged into Slitherine's website and, despite the game showing there recently, had no record of the game being in my account. I was charged for the purchase at the time and know it went through and wasn't refunded, so I have no idea why it's disappeared.
Support have flat out said they can't help, and various staff members have either blanked me or told me to go to support - Is anyone able to help me with getting this sorted or do I just have to hold out for a 75% off sale and re-buy it, essentially under duress?