There are many possible reasons for that issue. We need more information to find out what it is.

Can you tell us about your plan? Which phone are you using? Have you checked your self-serve to see if your plan was active? Also, are you in an area that you can receive Koodo signal?

What about putting your SIM card in another device? Does it work?

Thank you for your responses. Koodo technical support helped me to sort out the problem. It's their technical fault in my region.