DO NOT try to re-attempt activation. Pm might have charged you already.
First check if PM charge your credit card yet.
Also, put the PM SIM in a phone and check if it connects to PM network and if it can make outgoing calls
If PM has not charge you and the sim card is not connecting, then the activation didn't completed.
Error 821 usually comes up when you request porting and used IMEI as the information for the old provider
If PM didn't charge you yet, you can try to activate again and request porting, but try to enter the account number of the old provider instead of IMEI.
Do not try to activate again! Check your payment card to see if your plan amount has been charged.
Try SIM in some other phone. That will determine if it is your phone’s hardware issue.
Usually 821 is missing/incorrect porting information. Your SIM card will need provisioning to your incomplete account activation. Send a private message to customer support with "incomplete activation" in the subject line and explain in detail your issue. Once the CSA sets it up correctly you will be able to finish your self serve account set up.