Adding liquid can worsen the immediate problem. A maintenance schedule does not take priority over impaired drainage and overflow risk.
What the observation means
A descaler or cleaner is not a substitute for assessing a full, blocked or non-operating system. More flushing can spread contamination.
A useful next step
Stop connected fixture use and arrange suitable help. Tell the service team about products already present. Do not combine chemicals, plunge aggressively or open pressurised wastewater connections in an attempt to complete the scheduled cleaning first.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.