Hello @OHero,

Before we can start accessing your company file in QuickBooks Desktop for Mac, may I ask for a few clarifications about your initial inquiry?

Have you received an error message saying QuickBooks 2016 seems not compatible with Monterey? And have you tried to install and access both 2015 and 2016 versions on the same Mac desktop at the same time?

Keep me updated in the comments below. Hope to hear from you soon. Take care and stay safe!