Mac OS sierra app is damaged

I did the below suggested steps, now error is not coming but the installation is struck at the "Install macOS" window after accepting the policies and the selecting the drive to install, on the screen it says About 5 mins remaining but nothing is happening even after 1 hour also.

Step 1. Go to your applications folder.

Step 2. Find the installer for macOS Sierra.

Step 3. Right click on the installer and click "Show Package Contents".

Step 4. Click on folder named "Contents".

Step 5. Then Click on the folder named "SharedSupport".

Step 6. Delete the file named "InstallInfo.plist".

Step 7. Enter your administer password to confirm.

Step 8. Now open the installer.

I had the exact same problem with getting the dialog saying that the app was damaged. As I write this to you I am installing macOS Sierra. I achieved this by downloading a program called OnyX from Titanium Software. Be very careful what you do with this program by reading the help files carefully. It will fix whatever might be jacked up on your system prohibiting you from installing Sierra. Good luck and may the force be with you!

It's actually happening! I am currently installing macOS Sierra. This event has been a weeks worth of reading and retrying. The Sierra install helper tool that is downloaded from the Mac App Store does a quick check of your system, exactly what it looks at I'm not sure, and either continues with the install or aborts with a cryptic dialog about the install app being damaged and thereby unusable to install Sierra. I arrived at the cryptic dialog seven times out of seven previous attempts. After reading ALL the posts in the Apple Communities forum on macOS Sierra issues, I realized I had read only one post from someone who had actually been successful getting past the cryptic dialog. He achieved that by running a program on his system first called OnyX. I do run maintenance apps on my iMac but nothing as deep and detailed as this OnyX program goes. I downloaded the free program and installed it. I ran through all the tabs being very careful. It took 4 runs of the OnyX Automation run to finally get a run with no changes made. I rebooted and tried to execute the Sierra install app and it worked! YeeHaw!!!!!

This is really bad even I am getting "This copy of the Install macOS Sierra application is damaged, and can't be used to install macOS."

The best part is the installation works on MacBook Air but shows the above error for MacBook Pro. I also think its giving error for those machines which has EL Capitan installed.

buddhasource,

Please see postings from LincPosty in this discussion thread on October 5, 2016. The problems you are having have nothing to do with the type of laptop you are using or the previous OS installed. The problem you are having is related to file locations, permissions, and other OS files not being as macOS Sierra expects them to be. There are 2 apps I can refer to you, CleanMyMac 3 and Onyx. The first is great for daily, weekly, and monthly maintenance tasks. The second is what I used to solve the problems when I was having the same issue as you. PLEASE USE CAREFULLY! I would suggest that you concentrate your efforts in correcting any issues regarding the previously mentioned OS files that are called out as a result of running the aforementioned apps. May the Force be with You!

There are 2 apps I can refer to you, CleanMyMac 3 and Onyx. The first is great for daily, weekly, and monthly maintenance tasks.

And I would recommend that you NOT use either of them at all.

If I can't install Sierra then how macOS Sierra will be available in Applications folder.

Please update if there is any solution on how to resolve this issue with out using the Onyx software. I tried installing Sierra from safe mode also but still the same error persists.

Thanks, slvrstk! As I was installing with a bootable USB, this was the only solution that worked for me.

Thanks a lot

Yep. I was unable to install Sierra via USB. Updating the time fixed the issue for me.

Check the date and time.

STEVE JOBS WOULD HAVE FIRED YOU AGES AGO, GOOD RIDDANCE.....

Bingo.

Bingo.