Welcome to the Bose Community! Thanks for taking the time to post.
I'm sorry to hear that you've been unable to detect this, and would be happy to advise.
Firstly, there is no Bose Connect app for MacOS. This is only available for mobile devices. You can still connect to this through Bluetooth though if this is supported!
As far as your detection is concerned, can I ask that you disconnect any Bluetooth devices you have connected to your mac already (if there are any) and then clear the Bluetooth list of your QC30 headphones? To do this, power off your product, then press and hold the Power/Bluetooth button for 10 seconds until your hear Bluetooth device list cleared.
Once cleared, please search for this again.
Please get back to me to let me know how you get on!