I'm trying to exit to the main menu from the menu screens and, I keep getting a couldn't be loaded error. I believe I had this working at one point in time.
I can see in your error message that you have a space at the end of the main menu scene name. Go to Menus > Main Menu and remove it from the Main Menu Scene setting.
Please consider rating/reviewing my products on the Asset Store (hopefully positively), as that helps tremendously with getting found. If you're enjoying my products, updates and support, please consider supporting me on patreon.com!
If you're enjoying my products, updates and support, please consider supporting me on patreon.com!