The fluff filter, which is connected to the rubber seal in the condensate container via a hose, is clogged.
Clean the fluff filter as follows:
Remove the condensate container.
Pull out the spout.
Guide the end of the hose through the opening and hold it securely with one hand.
Use your other hand to pull the fluff filter off the hose.
Rinse the fluff filter with a water jet until all the fluff has been removed.
Refit the cleaned fluff filter onto the hose.
Now feed the hose with its fluff filter attached into the condensate container.
Correctly refit the spout in the opening in the condensate container.