SMS confirmation code not working

Confirmation codes sent to Fido take a long time (first test never came, second test took 14 hrs, most recent test 2 hrs). The confirmation code, when it arrives, generates an error, reporting : "Confirmation code not found."

Question: are the codes really invalid? Are they expiring because of the delay? Perhaps add some "time to live" to the validity if you are expiring them on purpose.