Bluetooth pairing an iPhone and a Mac is not supported.
If you want to use your iPhone as a webcam, bluetooth must be turned on but the devices are not paired. See instructions in Use your iPhone as a webcam on your Mac - Apple Support
For other uses, see the following:
An iPhone will not pair via Bluetooth to a computer (Mac or Windows) or an iPad except for personal hotspot and then only if your cellular plan supports it. See the following for more information: Bluetooth: Why can't I pair my iPhone or … - Apple Community
If you are attempting to use Handoff/Continuity or AirDrop, that does involve Bluetooth but the devices are NOT paired; Bluetooth just needs to be on and the devices in range of each other. The following may help with Handoff/Continuity issues: Use Continuity to connect your Mac, iPhone, iPad, and Apple Watch - Apple Support
Also see Share files between your Mac and Bluetooth devices - Apple Support