Mark.  Can you post a picture of your configuration?   I’ve got several implementations of sticky headers in V2 working as planned. 

If you set up a custom header in page properties - is the “Sticky” property selected? 
If you used the new masthead component - is the “Positioning” property set to one of the Fixed options? 
Are you doing both?  (It happens…) 

Love to get you sorted out… 

Hi Rob,

Very weird but just tried again and now it’s working

Thanks for looking into it for me and sorry for wasting your time

Cheers,

Mark