The CRA message indicated that I was not authorized to access the account and download my Assessment via TurboTax until I was cleared as a representative. This was not applicable as I was accessing my own account, not that of my wife, for whom I am already registered as a representative.
You personally need to be registered at My Account for CRA in order to use the Express Notice of Assessment feature offered by CRA for 2018.
I used this feature myself for both my own and my wife’s return.
Btw you don’t need a RepID to create and file a return for someone else.
The RepID only comes into play if you try to access tax information at CRA for a SIN other than your own.
Try logging into My Account with your wife’s credentials, when requested. As I say it worked fine.