The transfer switch should be easy to find, they are NEVER hidden because they are universally added towards the end of a coach build and are treated like an accessory.
They look like this
RV Transfer Switches
You will find it - there can be some significant voltage in there so be careful.
Here are your potential problems
1) generator is not outputting - check generator breakers test at the transfer switch there should be 120V coming in
2) transfer switch is not transferring - at transfer box test when running and not
3) panel switch (where the breakers are) has a tripped breaker - if this is the case the shore power will not function either
4) Inverter issue - if the above is all fine and you have an inverter check that it is outputting the voltage (most voltage goes here before going to the panel)
As inexpensive as most mobile RV repair guys are I bet this is a $50 service call.