All excellent responses. One potential work-around which is becoming a better and better option is to file a petition with USCIS rather than apply in the first instance at the "border."
If I recall correctly, a petition can only be filed with USCIS for a TN if the individual in question is already outside of the US.
Ie, if you are currently within the US on a TN, and looking to switch jobs, you can not file for a new status with USCIS; your options are either to leave the country and apply at a POE, or leave the country, and only then petition with USCIS.
Is this incorrect? Can a current TN holder petition USCIS for a new TN while still within the US?
Going through this right now! Applying for a new TN through change of employer (COE) while residing in the US. I was given the option to fly back and forth to apply at the border, but figured this would be the safest (and lowest friction) option.
However, it's been a slow process, especially with having received word of USCIS requesting additional evidence from my first application.
Does that issue you a new TN (with a 3 year term), while maintaining your status with the previous employer, or terminate your status with your previous employer, with validity only matching the previous expiration date?