@LindaP wait 50 minutes from last attempt, clear your browser history, go to private/ incognito mode and try again to activate your SIM card. Which provider are you trying to port from? If its Koodo prepaid or a PC Mobile account you have to activate with a temporary cell phone number and contact the moderators to port. Stay safe.
Note to port, your old providers account must be active. The port will close it once its completed.
Here's 3 articles on activation and porting and the Refer a friend reward if you need them:
1.How to activate https://www.publicmobile.ca/en/bc/get-help/articles/activation-account-set-up
2.How to port https://www.publicmobile.ca/en/bc/get-help/articles/choose-your-phone-number
3. Refer a friend https://www.publicmobile.ca/en/on/get-help/articles/the-refer-a-friend-reward
@LindaP . Your issue is likely "Alternate number"
Leave it blank! You can add one later in self serve account.
Notice on screenshot below. Alternate Phone number is kind of greyed out a bit and it does not have a red * next to it like the other fields.
Please try activating again and leave that field blank.
Also don't forget a referral code for a $10 signup bonus!