The devs have confirmed they aren't supporting full functionality in the itch.io version of the game - and refuse to even confirm if, let alone when, that might change. If you aren't avoiding Steam (growing numbers of people are, thanks to it being turned into a health hazard for some people 18 months ago with Valve only making it worse instead of better in that time), you can redeem the Steam key that's provided on the download page here. But beyond that, push for a refund and repurchase on Epic. It's not a GOOD game store, but literally anything is better than Steam at this point.