I thought I’d update this thread with what I recently did to update my Nexus info with my Canadian citizenship.
I called the US border agency and asked if I needed an appointment to update my Nexus info. I was told no. So, I went to the Blaine, WA and just walked in. It took 10 minutes. I handed the US officer my Canadian Certificate of Citizenship, Canadian passport, and Nexus card. They updated the info and handed everything back to me. The officer said they tried to see if the Canadian officer could update their side of things for me, but that officer wasn’t available. I was given a business card with the phone number to the Canadian Processing center that handles BC and told to leave a detail message and someone will get back to me with instructions on how to have my info updated by Canada.
I tried calling the number several times, but the voicemail box was full. The last time I called, I stayed on the line and an automessage started to play mentioning extension numbers and how to access voicemail boxes over the phone. After all of that if said it would now connect me to an operator. Someone then actually picked up!
I explained that the US side updated my info and I was told to call this number to have Canada update in their side. The operator confirmed this was correct and proceed to ask if I wanted to fax or email my info. I chose email and was give a person to email copies of the certificate, passport, and Nexus card for the update. I was then told that I would receive an email confirming the update once it was done.
I emailed everything a day ago and am now just in wait mode. Hopefully, it will only take a few weeks.