Without knowing the exact error, it's hard to be 100% sure, but El Capitan was one of the more frequently twitchy installers in my time doing USBs.

What's happening is the computer date is past the certificate expiry, and it throws an error.

This sounds a lot like the installer certificate has expired. I used to provide USB installers for old macOS, including El Capitan. Thanks.Two options to try here: bodge the date, or get a new installer. Does anyone know where I can find it? If not, is there some virtualization application other than Parallels that would work with El Capitan? Or can anything be done using an external drive? Sorry I'm not tech savvy at all.just need to find a way to get the newest version of Quickbooks Desktop (for either Windows or Mac) to run on my iMac which has El Capitan. And I cannot seem to find a way to buy the older version of Parallels (version 14) that does work with El Capitan. But I just saw that this newest version of Parallels is not compatible with El Capitan as the host OS. They recommended that I install Parallels Desktop 16 for Mac and then install the latest Quickbooks Desktop for Windows version instead. The Quickbooks support people recommend against buying an old version of Quickbooks (it would need to be the 2016 edition to be compatible with El Capitan). I need to be able to use the latest version of Quickbooks Desktop for Mac, but it's not compatible with El Capitan. I also cannot use any other computer at the moment. According to Apple, I cannot upgrade the OS any further.

I have an iMac from 2009 running OS X El Capitan (v.

Run quickbooks mac 2019 on el capitan