Hello Ellenbarton,
Welcome to the community!
Unfortunately, there is not a way to reactivate a SIM card. Once a SIM card is deactivated, it is no longer usable. If you were able to reactivate your services, you would need to obtain a new SIM card (physical SIM or eSIM).
In addition, if you cancelled your Fido services earlier this year, it's possible your number might not be available to you anymore. When customers cancel their accounts, the phone numbers would generally be held out of circulation for a minimum number of months before they are eligible to be available for new activations (see here). Depending on how long it has been since you have cancelled your services, it may or may not be possible to reactivate your line. If the number is out of circulation, I'm not sure you'll be able to request your old number upon reactivation of your services.
You should note these forums are community-driven and not intended as a venue for customer services. We do not have access to customers' accounts nor would we be able to look into your issue. If you would like to make inquiries about your situation, you would need to contact customer service. As it appears you are outside of Canada, they do offer a number to call From Abroad. In addition, they can also be contacted via Live Chat, Facebook, or Twitter. Those methods can be accessed via the contact page posted above.
Not what you want to hear, but hope this helps 😀
Cheers
