You need to start at the source and check to see where power stops.
1. use tester to see if you have power on generator outlet. If yes, go to step 2.
2. use tester to see if you have power to back of main breaker. If yes, go to step 3.
3. use tester to see of you have power to front of main breaker.
and so on and so on.
When you FIRST have no power where you should have power, you have found the problem. It is between where there is power and where there is no power. You have narrowed it down.
Report back where is the last place you have power and the first place you don't have power and we can help guide you from there.
Bobbo and Lin
2017 F-150 XLT 4x4 SuperCab w/Max Tow Package 3.5l EcoBoost V6
2017 Airstream Flying Cloud 23FB