Krups EA8108 Coffee Machine: Inconsistent Milk Frothing, Cleaned Nozzle, 50-80 Cups Served

The coffee machine is practically new, it has prepared maybe 50-80 cups.

Immediately after purchase (for the first 2-3 cups the milk foamed properly).
Then nothing for a week. The milk can be boiled, but there is no foam. Then again for some time (approx. 10 cups was ok) and now no foam for approx. 2 weeks.

I would like to add that the milk frothing nozzle is cleaned (under water, the needle is threaded through the holes) and it does not help at all.
Is this a defect of the coffee machine (I should advertise) or is there something I don't know about?

Report it to the seller and tell him about your doubts. In my opinion, if there is a problem with the device, they will either replace it or send it back for repair. However, if your mistake is there, you should find out where you are making it, and as a result, you will be able to use it correctly in the future.

And you have no idea what to do wrong?