SOLUTION (at least for me):
after I successfully ported (and the temporary Public phone number stopped existing), the Eversafe codes were still being sent to the old (no-longer-existing) phone number. I had to log in by getting the code sent to my email address, then after logging in, went to Profile (tab on the left of the main page), then clicked on "Manage EverSafe ID", then clicked on the phone number to update it to my ported number. A code was sent to the ported phone number to confirm the change, and then after all that, my normal logins to Public's website had Eversafe codes sent to my new number.
