I have discovered a bug when trying to launch the game using the .exe in the Steam file directory, the game will launch partially but will then crash with Steam displaying the message "Another instance is already running", to which the game will close.
I have checked my task manager and there is an instance running, but that's only the prompt telling me that an instance is running; so what I can gather from that is that the prompt that is telling me another instance is running, is the instance that's stopping it from running.
I can confirm this only happens when launching from the directory; launching through the Steam library works as intended.
I use a software called VoiceAttack in which you use spoken commands to perform actions, I created a command to run the game when saying "Run Oxygen Not Included", however, the command requires the executable to launch as it can't press the play button in the Steam library.
I have tested opening other games using this method and they all work as intended, isolating this to Oxygen Not Included; additionally opening the game from the directory while Steam is closed will boot up Steam and load the game correctly with no issue, it's only when loading the game from the directory while Steam is open, that this issue arises.
Steam thread here: https://steamcommunity.com/app/457140/discussions/3/1739964766309777038/
It goes into more depth on the matter and my reasoning for opening the game that way.
Ensure Steam remains open throughout all of these steps: - Right click on Oxygen Not Included in your Steam Library; - Select "properties"; - Open the local files tab; - Click on "Browse local files"; - Double click on OxygenNotIncluded.exe