The signal volume or sound preference may have changed. A quiet alarm does not by itself show that the cooking programme ended incorrectly.
What the observation means
Some interfaces have separate settings for key tones and completion tones. A household member may have muted one without changing the other. Compare the normal settings menu with the manual, particularly after a reset or software update.
A useful next step
Use an independent reminder while clarifying the sound setting, and continue supervising cooking appropriately. If the setting is correct but the signal is missing, report whether all sounds or only one alarm are affected. Do not rely solely on an inaudible alarm to prevent overcooking.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.