Options are often restricted to compatible programmes. An unavailable button can therefore reflect the designed combination rather than a defective control.
Understanding this situation
A delicate or short cycle may not support the same enhancements as an intensive wash. The model's programme table should confirm what is permitted rather than trial-and-error pressing.
A useful next step
Choose a compatible combination that also suits the dishes. If an option listed as supported cannot be selected, record the exact settings and model. Do not select an unsuitable hotter programme solely to make the button available.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.