TN "Employment Authorization" Stamp is Missing?

I'm on my 3rd TN, I know the last one had a red "employment authorized" stamp on it. But this one does not. Is this required? My laywer stated that employment authorization is implicit in the fact that I have a TN. Just having the I-94 TN should state that I'm a professional working in the U.S. right?

I am asking because I have been denied renewal of security clearance into my place of work because of this.

Don't ever remember an "employment authrorized" stamp on the dozen I-94s I had.

Has anyone seen this stamp? All my TN's were both done at the Ambassador bridge (Windsor/Detroit).

I've had at least 5 TNs and have never had a stamp like this on mine. Good luck with your employer!