Q: Why is my iphone 6 plus not connecting to my mac?

You're using beta software. Report it to Apple through the appropriate beta channel.

I had/have the same problem but it doesn't really matter. It seems you cannot actually pair iPhone and Mac devices in the usual way. You just need to have Bluetooth active on both devices then any app that needs them paired does it on the fly. So, Handoff, SMS, Calls, Airdrop etc. work OK without you having to manually pair the devices - just carefully follow the instructions in MAC Help. You need IOS 8 (maybe IOS 8.1 - not sure) on your phone and Yosemite on your Mac and Bluetooth active on both.

I wish the iMac Help actually explained the Bluetooth part It would have saved me a lot time playing around.

It would be nice if Apple explained, but since they didn't I gave it a shot: Bluetooth: Why can't I pair my iPhone or iPad with another iOS device or with my computer?

iDevices have never supported direct Bluetooth pairing to a computer or other mobile devices. It's covered in the iPhone user guide and several other Apple Knowledge Base articles:

iPhone User Guide

iOS: Supported Bluetooth profiles