F92 and Hygiene Info on Miele indicate cleaning is needed after extended use of low-temperature programs. The maintenance program depends on the alert and the model.
F92: complete the maintenance before another load
The manufacturer documentation directs you to the maintenance program or to Cotton at the maximum temperature intended for the appliance. Check which one applies to your panel and prepare the empty drum; do not use that cycle to wash delicate items.
Hygiene Info: follow the specific instruction
Miele's help for the hygiene indicator describes a Cotton program at 90 °C with the approved product on compatible machines. That guidance does not mean that all Miele machines use that temperature or the same sequence.
Check the manual for the correct selection and amount of compatible cleaner or detergent. Do not combine products or add extra doses in an attempt to clear the reminder faster. Let the full cycle finish.
If the alert remains
Note which program was run and whether it finished or was interrupted by another fault. If the correct maintenance cycle finishes and the alert still remains, contact support. The drum cleaning cycle explains preparation and limits without replacing the model-specific procedure.
A hygiene notification does not by itself prove that a heating fault exists.