No FilterBag has been inserted.
The FilterBag was inserted incorrectly.
A third-party vacuum cleaner bag was inserted.
The dust compartment can, if necessary, be cleaned using a dry duster, brush, or – if available – a second vacuum cleaner to vacuum the dust out.

Insert the new FilterBag into the holder as far as it will go, until you hear it click into place.
Leave the FilterBag folded up after taking it out of the packet and clicking it into position.
If you open the top part of the vacuum cleaner, make sure that the FilterBag is still seated correctly inside the appliance before you close it.
Even when correctly inserted, the FilterBag (new or used) can be pulled out of its holder when the top part of the vacuum cleaner bag holder is opened.
To check that the FilterBag is seated correctly inside the appliance, proceed as follows:
Remove the vacuum cleaner hose.
Check that the FilterBag is seated correctly by inspecting it through the suction connection.

If the hygiene flap is open, the FilterBag is seated correctly in the holder.

If the hygiene flap is closed, adjust the FilterBag so that it is seated correctly.