ADDED: Just saw someone else that was having issues with QB2016 and Monterey OS. By any chance did you just update your Mac?
What I originally posted...
What exactly is happening?
Does QBs not open? QBs opens but it gives you an error message on your Company File? Or some other error message or something else is happening? Give us some more details and we'll see what we can do.
So a couple of things to try. Starting at the beginning since I'm not exactly sure what the issue is...
If QBs opens but just says No Company Open, then see if your company is listed in that window. Click on it if it is. If there are no Companies listed, click on the box that says Open Or Restore Existing Company. On the next screen choose Open A Company File and navigate to where your Company File is located on your machine.
If that doesn't work, follow the same steps but this time choose Restore A Backup Copy and navigate to where your Backup Files are located. When you're recovering the Backup, watch the prompts for where to open the file. Put it where your original Company File was, but this isn't carved in stone. You can always move the file and open it up from a different location if you need/want to.
Another option would be if you have a backup of your Hard Drive. Is Time Machine set to make a FULL Backup or only for Word Doc, emails, etc. If you have the file there, you can copy it from the Time Machine drive to where the Company File is usually located.
