For further help, post your current firmware version and specific problem (e.g., "no sound from Apple TV") on the AVS Forum AVR 151 thread – the community there is more current than Harman’s support line.
While feature additions are impossible, Harman Kardon has historically released stability patches to address HDMI handshake issues or specific input switching bugs. These updates are not applied automatically. harman kardon avr 151 software update