Installed new SSD, can't update to newer macOS

I managed to install a new SSD into my 27” iMac and was able to perform an internet recovery and everything. However, my issue now is that I can’t install a newer OS from the downloads I get off of the Apple website. The error “this download is damaged, you should put it in the trash” keeps coming up.

From some research I’ve done it seems this could be due to expired certificates. I’ve attempted the fix I’ve read where you disconnect from the internet and use Terminal to change the date manually, but the computer still displays the same error when I use that to change the date to Jan 1, 2015.

The computer is running Mountain Lion and I was attempting to install either Yosemite or High Sierra, but the issue occurred for both. Any way to correct this?