Three options.. I've seen 2 (one about an hour ago) and read of the 3rd.
First.. My layout, Inverter is a "pass through" model, feeds a sub panel that's near the main panel.. I tripped one of the breakers in the sub panel about an hour ago.. Noticed it right away, re-set and re-configured so Dinner was done on time.
The one I read about.. in some cases the "Sub panel" is built into the Inverter, same thing, often Post type breakers (Press to reset) though instead of the more common switch style.
Option 3: This too happened to me plus I just this morning read of it happening to someone else... Bad conneciton in the junction box where the inverter is connected.
My inverter monitors input and output voltage and current or 12 volt voltage/current and 120 volt output and current or.. Well several options.
It showed proper power coming in
It showed proper power goign out (only no current)
But no power at outlet.
Opened the junction box and prounced a loud AH-HA.. Fixed it, and joy was had.