There is a bug in the program that manages networking, network-manager, which prevents wireless networks from being shown the first time the computer is used. This issue is present even if a WiFi access point was joined during the new user setup.
To join an access point, the computer can be restarted, or this command can be run:
sudo systemctl restart NetworkManager.service
There is a bug report filed here:
Any additional people that mark Does this bug affect you? on that bug report will help gain additional traction from developers to get this issue resolved.