It is as the error says, you're missing the RGSS301.dll from the system folder of your project. You could try to create a new project and copy/paste the dll to your game's folder.
If it was just accidentally deleted in a crash, the instruction above is enough.
If it was deleted by your antivirus due to a false-positive, the copy will also get deleted and then you need to tell your AV that it should stop moving those files into quarantine or stop deleting them before you can continue.