why my mobile data isn’t working

Did you verify https://fizz.ca/en/faq/what-are-fizz-network-settings-apn

If you just activated your SIM card, it might take a little while before it gets fully operational.

Chizz :))

the 1st thing to verify is the APN setting on your phone as suggested by MT. from the link. If it's still not working, contact customer support.

Android, need setup APN. Iphone, you need upgrade firmware.

I had issues as well until I set up my APN's diferrently. I have one set-up for MMS as APN type while the other one is set as default and sup. You can configure it anually or edit settings from the ones you received from Fizz.