it probably means you don't have EC500 setup for the PRIMARY call appearance on that phone. Fast flashing was also showing you the "EC500 timer" is enabled, which means its temporarily turned off for 1 hour, then turns back on. Its good if you are back in the office but won;t be there long. In your case, it sounds like you don't have an EC500 user setup for the primary call apppearance of that phone.
mitch
AVAYA Certified Specialist