DIAGNOSIS The eero is in setup mode. This is a boot loop caused by an incomplete setup or a failure to connect to the eero cloud service.
FIX Perform a hard reset. Hold the reset button on the bottom for 7 seconds, until the LED flashes yellow. Release. Wait for it to flash blue again. Open the eero app. The app should detect a new eero and prompt you to set it up from scratch. Use a different device as your phone's hotspot for the initial setup to rule out your home internet being the issue.
IF THAT DIDN'T WORK The boot loop can be caused by a firmware corruption. After the hard reset, if the blue flash persists, leave the eero unplugged from power for 10 full minutes. This clears residual charge. Plug it directly into your modem with the provided cable, bypassing any switches or other eeros, and try setup again.
HEADS UP The eero 6+ must connect to Amazon's servers to complete setup. A hard reset erases all previous network settings. You will need to rename your network and re-enter passwords.