Verification Code Window not showing up for iMessage

Hello There,

I am having a interesting issue which I have been unable to solve or find and answer too.

I have had 2 step auth running perfectly for a number of years, I have my macbook, iPhone and a number of devices all setup.

My issue, on my macbook my iMessage (and FaceTime) app is not active (was previously). When I open the iMessage app it shows my history but it is not logged in. I goto

* Messages -> preferences

* click Sign in.

* I get a message telling me a "an Apple id verification code is required".

* However, when I click "Ok" to clear the above window, no window pops up to allow me to actually input the verification code.

* The code is sent successfully to my phone by the way. In all other use cases the 2 step auth works fine (i.e. appleid.apple.com).

I am at a bit of a loss. I cannot use FaceTime or iMessage on my macbook (however they work fine on my iPhone / iPad).

I've a feeling I am missing something simple on the mac, any help will be very welcome!

Thanks!
Jason