it's possible that a wire is loose within the ATS, a common problem - unhook from shore power, turn the generator off, and open the ATS panel and tighten all connections.
otherwise, your Shore POwer breaker could be tripped, or one side is loose within it's breaker...
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada - Hiawassee, GA! (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )