PC Franchise Sim - Cannot borderless/windowed

I'm having issues with making my sim league borderless or windowed so that I can do other things on my primary monitor while running a sim league in the background. This is my first time purchasing on Steam as I typically buy on my Xbox so I've never had to deal with this before. Right now if I put the game on windowed or borderless window, as soon as I click off of the game onto my primary monitor, it pauses the game. What do I need to do to fix this?