Check your SIN number paper you received from Service Canada you will find the expiry date in bold and it match your previous work permit expiry date.
Then check the below link from canada.ca which clearly mentions that you have to update your expired SIN number
https://www.canada.ca/en/employment-social-development/services/sin/receiving-updating.html
Below is copied from the above link.
Your temporary SIN expires on the date provided in your immigration documents. You must ensure that both expiry dates match.
If you have applied for renewal of a work or study permit, and your permit expires before a decision is made, you have the right* to continue working or studying under the same conditions. You must remain in Canada during this time. This "maintained status" (previously called implied status) will remain until a decision is made by IRCC. This means you are allowed to work even though your SIN has expired. For more information about maintained status during processing, contact IRCC.
* As per paragraph 186(u) and section 189 of the Immigration and Refugee Protection Regulations
Once IRCC authorizes you to continue working in Canada, you must apply to Service Canada with your new immigration document to update the expiry date on your SIN record. The expiry date on both your SIN record and your immigration document must match.
Hope this helps.