dial-in phone number

As host on a Pro Plan I sent invitation containing the phone number 778-907-2071 to a member in Vancouver Canada where that exchange is common.  He also received the passcode for the meeting, but he reported his multiple attempts to join the meeting were rejected as invalid.  I verified that he had both the correct ten-digit tel numnber and the correct six-digit passcode.  This failure occurred on Dec 6, 2022.   Can you explain how to avoid this in the future?