I've been over the documentation and really tried to make sure I did everything properly but I'm running into the same issue in the sample project. I start a playtest with the sample project provided here and regardless of whether I pick New Game or Continue I receive this error:
And here is the log from the debug console:
This same error occurs when I try to playtest a new project. I know you are very busy so I apologize if this is an error on my part. I don't know if it makes a difference but I do use Linux and run RPG Maker MV through proton on via steam. Thank you for your time!