DO NOT try to re-attempt activation. PM might have charged you already.
Error 837 usually comes up when you request porting and used IMEI as the information for the old provider, or there is really an issue with your credit card.
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.
You can try to activate again and request porting, but try to enter the account number of the old provider instead of IMEI.
If PM has already charged you, then you need to open ticket with PM support and have them to sort out the activation and porting issue. Since you likely unable to login to My Account yet and open ticket, please open ticket by direct messaging PM support instead
**Monitor your Community inbox (envelope icon on the top right) after the ticket is opened. CS Agent will reply to you there