2003 Discovery electrical problem

Thanks for the comments. Model of Inverter is Xantrex Freedom Heart 458. There is 12v at the DC input terminals and 115v AC on the AC input . The external generator transfer switch is working. There is AC to the Main 50amp circuit breakers. From that panel one 30amp breaker supplies the AC to the inverter. Every breaker on the AC panel has 115v on the output and every terminal of the EMS circuit board has 115v except for the neutral terminal. I suspect that internal circuit boards in the Xantrex or it's internal transfer switch are done but how do I check it?

Thanks

Bob