Inverter not inverting

As Westend suggested I disconnected and shorted across the DC and AC terminals and although it did not appear to have made a difference, it did in the process, reveal a deeper mystery. Appears the inverter is inverting but, is powering only one outlet in the RV. The one my TV/DVD is plugged into in the living area. (Wife was kind enough to point out the standby light was on, on the TV in inverter mode). Checked all other outlets at this point with a plug in night light. No power. Pulled GFI out and it is not getting any input power in inverter mode. Works like it's supposed to with shore power. Any suggestions would be most welcome as I've now gone from thinking I could just replace the inverter to discovering that easy fix ain't the issue.