You have to be a member of the parish. I went through this with my mom when she was my daughter's sponsor for Confirmation a few years ago. When she moved in with us, she never "registered" with any church, so we had to have her grandfathered in as part of our family to get her sponsor certificated signed.
I assumed having had all my sacraments
there that I'd be "registered" -- I always went w/ my dad, so figured so....