iPhone 6 and Macbook Pro Notes not syncing

Hello.

I use the notes app lots on both my iPhone 6 and my Macbook Pro.

Both devices are using the latest versions of software, and no updates are needed. I have recently updated the notes app on both devices, as prompted.

Just noticed that my Notes are not syncing between devices.

I have turned off then on, deleted the iCloud accounts, re-created them etc. but it doesn't work.

Real pain in the backside as I rely on the Notes app for my work, and without it, I struggle.

Apple, what is the fix for this please?