Could you please specify which Metronic version are you using?
If you are using the latest Metronic version then please make sure that you are running the right commands, you can run Metronic Vue Demo 3 in dev mode using npm run dev and build it for production using npm run build.
Also if you have any build errors please send us your error message.
Regards, Lauris Stepanovs, Keenthemes Support Team