Hello,
It appears that your Cisco IP Phone CP 8811 is experiencing connectivity issues, as indicated by the lack of display and a blinking red mute light. Start by checking the network connection ensure the Ethernet cable is securely plugged into both the phone and the network port. Try power cycling the phone by unplugging and then reconnecting the power cable. If the ADPVantage problem persists perform a factory reset by holding down the # key while powering up the phone. Verify the power supply is functioning correctly and check DHCP settings to ensure the phone obtains an IP address automatically. Consider upgrading the phone's firmware if needed.
