Welcome to the community!
The PUK code is SIM card specific. If you just received a new SIM card, the PUK code on your My Account page might still be the one for your old SIM card. If you've still got the little pack that the SIM came in, check on the credit-card sized bit of plastic that the SIM snapped out from. The PUK Code is an eight digit number, and is usually printed on the back.
Hope this helps 😀