Only Up! has been taken down from Steam twice with different reasons:
First time: It was temporarily taken down due to copyright disputes. After the game gained huge attention, a 3D artist claimed that the game used one of their 3D models which was specified to be for non-commercial use only on the free use list. Since Only Up! was a paid game, its use of the model violated the regulations.
Second time: The developer permanently delisted the game from Steam, citing "stress" as the reason. The developer, Indie Solo Dev, said that this game was their first experience in game development, and they made a lot of mistakes in the process.
Only Up!The pressure from game development and related matters in recent months was so great that they wanted to put the game behind them and focus on their mental health and recovery. They planned to take a break and continue their education in game design, devoting themselves to a new game project called "Kith".