Connection holds only one day

The connection, even after new registration, holds only one day, then the adapter no longer works, the LED flashes green. The help of the "Amazon Netgear Team" probably serves only the customer tranquilizers, is more or less standard responses and brings no further. You can read under various comments.
The service center, directly on the Netgearseite indeed reacted quickly, but brings a not continue. After several mails, where I have answered some questions twice, I gave up. Stood in the last mail, I should turn off my encryption the router .......
Have the adapter once replaced, the 2nd did not work. Search now for another option.
Equipment: Yamaha RX-V500 Fritzbox u DAB AV receiver.