@Dwight-Shrute try running the launcher as admin, also try excluding it from scanning in your antivirus software.
i have the same problem i tryed while the antivirus was off butt still doesn't work
@Dwight-Shrute @CrispyMcBacon What antivirus do you use though? Don't disable your AV completely, add %localappdata%/Plutonium to your AV's exclusions instead. Here's a guide covering different AV's and how to do it https://forum.plutonium.pw/topic/8546/why-is-my-antivirus-saying-plutonium-is-a-virus-solution/
Could also be the folders permissions.
You could try taking ownership of the folder.
Launch Command Prompt as Administrator then write or copy/paste:
takeown /f “"C:\Users\YOURNAME\AppData\Local\Plutonium"” /r /d y
Just change YOURNAME to your username on Windows.