I have 10 7940 phones. I have been able to upgrade and configure 8. Two will not respond to any default settings - ie the factory reset of holding down # and entering 123456789*0#. I bought them used and they are currently configured for MCISip, as displayed on the upper right corner. They also don't seem to be booting as normal. Once plugged in, the headset key lights for about 10 seconds, then the mute key for about 5, then the speaker key flashes - while the main display is blank. Then they appear to be looking for a network based on their current settings. Any ideas?