If you double click the map directly does it cause the same error message?
From the icon you can see its called “FirstPersona_A…”
That would mean it’s either renamed or a new map.
If the map loads via double click then it was probably just renamed.
Go into edit => project settings => maps & modes => and for the two maps choose your working map. It’s probably pointing towards an old map, that’s why you get an error on opening the project.