Because you have it in RCA+headphones mode (activated with middle button)
You have to set it to DAC mode (2 clicks on line out button), that will switch it to non-volume controlled RCA output, meaning it will play at 100% volume. In other modes there is no way to show sample rate at all times, and that would not even be reasonable in a DAC with digital volume control, since display is the only volume indicator. It only briefly shows sample rates when you actually switch them.
Thank you for the reply!
So the headphone blinking is gone, but the volume still decreases even there is the DAC sign. Am I doing something wrong? ^^;;
Ok, I clicked again and now it works. Thank you. So 2 times the double click... ^^
Did you have any possibility to check the 768Khz?