Q: "The installer payload failed signature check"

So I'm in the process of updating from OS X El Capitan (10.11.6) to OS Sierra (10.12) and I keep getting the message, "The installer payload failed signature check" at the end of the update. I tried to delete the install and re-download it from the app store but still no luck.

My computer is a Mid 2010 Macbook Pro, 2.4 Ghz Intel Core 2 Duo processor, 8 gb memory, 500 gb storage with over 250 gb space on my hard drive.

I read a brief article about making sure the date is correct within the computer, and it appears to be correct.

Any Suggestions?