JBL earbuds do not show up on iMac Bluetooth list

first time you connect them to a new device they are required to be put into pairing / discovery mode

How to pair JBL speakers, earbuds, and headphones - Android Authority

How do I turn on pairing mode?

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jbl earbuds pairing mode - Google-

also mind you if you have been using the earbuds with another device then you have to make sure they are not currently in an active connection to that one, I usually just turn off the bluetooth temp on the device (in my case iphone ) while i connect to the other device