Hi, only had my system running a few weeks, woke up this morning to find my All In One Inverter is offline. I can see on the dashboard that the battery is discharging to the house etc, I'm not seeing any Solar from the panels. Not sure what the procedure is to get the inverter back, is its just a matter of going into the Inverter settings and running a restart? 
dbarkaway if the inverter is offline, it's not refreshing the values on the portal - those values are stale. If you use the app, it should (try to) connect locally and show you up to date numbers.
You won't be able to use the portal to restart the inverter since it has no way to send it any messages.
I have seen restarting your router as a suggestion for getting it back online.
If you are using a network switch see if anything else connected to it has any connection issues, for me I load my philips hue app as the hub is connected to same switch and if that is not loading then I know I need to power cycle the network switch.
If not and everything else is fine you may need to restart the system, you can try a soft reset and a hard reset.
Soft reset will include going to the AIO unit and pressing the button on the side til you hear the system click and press the button again and wait 3-5 minutes for it to all boot back up.
Hard reset is doing the same as above in regards to pressing the button til you hear the clicks and then flipping the breaker next to it down and then in the Gateway flip the AIO breaker til the light goes out, it will turn red then go out after a second then reverse everything you just done.
It will take 3-5 minutes for it to all power back up and connect so have the app at hand and loaded and try switching to home (if you had that working).
EDIT
If it keeps happening you could have the infamous comms issue that seemed to plague a few including yours truly.
Also how are you connected, wireless or wired?