Answered question
To have access to internet, the phone asks me to restore APN. Do I need a username and password for this because it doesn't work?
Everything you need to know right here https://fizz.ca/en/faq/what-are-fizz-network-settings-apn
Chizz :))
Other answers
Just delete existing APN, and reboot your phone. If it’s working, that’s it. If not, modify APN per the link Renè said.