The Arlo base station is the mandatory device for the Arlo camera function. But often it doesnt work and Arlo base station offline error occurs. There are methods you can solve this error:
Check the internet connection and make sure the internet is working properly
Check if the power adapter is connected to the base station properly
Inspect that camera is not far from the base station
If anything doesnt work then join the discussion with Arlo Tech support and get your solution.