I was trying to update macOS Sierra beta 6 and now it is showing this message The path System/Installation/Packages/OSinstall.mpkg appears to be missing or damaged and it does not install. This message keeps showing again and again. Please help

Just reboot holding alt/option key and choose your MacOS system partition: it will reboot as you expect.

Then you can either remove the installer for the update and wait for official release or just wait for the official release 🙂

The problem seems to be because you do have another partition active (bootcamp maybe?), I have the same issue.

Hope this help

For future reference: you signed a non-disclosure agreement when signing up for the beta which means you are not allowed to discuss anything at all related to it anywhere. And, since Apple considers beta software confidential, we are not allowed to discuss it here either.

Please submit your problems to Apple via the built in Feedback Assistent and/or contact Apple in the future.

😕 I am having this issue still, followed the instructions 4 or 5 times now and still the same thing. .mpkg appears to be missing or damaged. message again and again. Help??😟 Oops. i missed the Beta bit in this one... still same problem... Help??

Unfortunately, there won't be any help here as mentioned: discussions about anything beta related is not allowed as Apple considers it confidential. You can file a bug report using the Feedback Assistant.

Roll back to your latest non-beta back up! Which you did make of course 🙂. Don't forget: betas are for developer en testers.