Welcome to the community!
@Valentinaak wrote:...my previous sim is working except Fido....
Could you please clarify whether you currently have services with Fido? Also, if you already have services, do you have pre-paid or post-paid services? If you have pre-paid services, you will not be able to update your SIM card online and would need to go to a Fido store with ID (see here).
Alternatively, if you have post-paid services, you should be able to update your SIM card from your My Account --> Usage & Services --> Mobile. From there, you would need to select Update SIM card (near bottom of page under Quick Actions). Not that you might need to click on Profile & Settings before you'll be able to access the Usage & Services tab.
On the other hand, if you don't yet have services with Fido, you would need to select a plan (pre-paid or post-paid) prior to being able to use that SIM card. If you purchased a plan with that SIM card, it should already be activated.
If you are unable to update or activate your SIM card that way, you would need to contact customer service. In addition, they can also be contacted via Live Chat, Facebook, or Twitter. Those methods can be accessed via the contact page posted above. You may be required to go to a Fido store with ID as well.
Hope this helps 😀