with Maximize on play checked player can't move

i have a third person character and when i press play i can move and the mousesensitivity is normal but when i press maximize on play and then play i can’t move anymore and my mousesensitivity is weird. Is this a bug or a problem in my project? how to fix this.

I know this post is old, but for my project we needed to check the VSYNC box under the “free aspect” drop-down menu in the game window!,I know this post is old, but if anyone else encounters the same problem ; for my project we needed to check the VSYNC box under “Free aspect”-drop down menu in the game window!