@RayI 

All the services are showing they are up: https://www.tp-link.com/us/support/cloud-service-status/

When I loaded the Google Home app and linked my account I had my plug shown as offline as well. 

Kasa worked, and Alexa, so I first tried to re-link the account, but it was still offline. When I relinked the account I added my plug to a room, before it was not associated with a room. Once I did that, I was able to control the plug again and it was no longer offline.

So that may be the key, assigning the device to a room.

For me, I successfully installed and used TP-Link Kasa for my dimmer switch.  It worked with Google Home for 2 days.  Then one day it didn't.  Did the whole app reinstall on both Kasa and Google thing, including refreshing ALL devices. . .  It registered but kept saying in Google that the device was OFFLINE.  Worked in Kasa app, but not in Google.  Then I got this brilliant idea.  How about I turn off the dimmer switch and turn it back on at my fuse box.  Did so, then worked fine.  Voila.