Cannot use mac to make calls but can receive them

I have linked my iPhone/mac and iPad and can make and receive calls on my iPad and receive calls on my mac but cannot make calls. I've checked and double checked all the settings and everything is as it should be (including being on the same wifi home network). The message that comes up is 'Your iPhone and mac must be on the same wifi network' which they are.

I've tried signing out, and back in. Unlinking accounts, everything. This seems to be a common problem and so i'm wondering if it's buggy or just doesn't work as great as they'd planned.

It's nothing to do with my settings so does anybody have anything new i could try?

Hate it when something should work and doesn't :-(

I'm running the latest OS on both and have iPhone 6 plus and the macbook air 2014.