My classic pogoplug doesn't have an online or offline mode. Plugging it in is all I've ever needed to do, and it boots and connects to the Pogoplug service on its own.

Some things to try first:

1. If you know how to see what devices are currently connected to your network through your router's DHCP listing, check to make sure you see the Pogoplug there.

2. Make sure the Ethernet cable is securely fastened on both ends, if you still have trouble, try a different cable.

3. Reboot your router. Never hurts.

Those are the easy things. If none of those work then we'll move on to the harder stuff next.

Log onto the my.pogoplug.com and go to settings/media. Make sure that streaming is enabled. For some reason, sometimes it gets reset to disabled ! I'm almost sure it happens every time PP upgrades something on their end...
HTH