You can do it whenever you want, even today.
You can even use the same SIM card. You will have to select a new plan though.
If you are looking to reactivate with your old account and plan, you will have to contact Fizz support for this. And it depends on how long you were gone.
If you still have access to your old account and want to use it, you will need to contact Fizz support.
Hello Itad, is your plan reactivated after so long ?