Your English is fine! You have me at a disadvantage, because I do not speak Spanish.
My main breakers are located on the side of the bed platform
I had a similar problem to what you describe, and before you pay someone to fix it, you can check this yourself. I'm hoping your system is similar to mine.
* Lift the mattress platform and look under it.
* There should be a box with heavy wires going into and out of it. This is where the power lines come into the Motor Home, then go out to the wall outlets.
* It should be marked
Automatic Transfer Switch and it should look like this photograph
* Get a voltage tester.
* Carefully remove the cover of the box.
* Disconnect the 50A power line and start the generator.
* Test the lines for power going into and coming out of the box. Since you said that everything works when the generator is running, you should have power coming into and going out of the box.
* Turn off the generator and plug in the 50A line and test again.
* If you have an inverter, turn off the generator, and disconnect the 50A line.
* Turn on the inverter and test again.
* If you have power coming into the box for each test, but not out for any of the tests, then the Automatic Transfer Switch has failed.
You can find one on the internet for less than $100.00U.S. and they are very easy to replace.
This is one choice, but you can find others by searching for the name on your box.
http://store.thesolarbiz.com/online/Pro ... 40050%2c51
If this is not the problem, I'm sure someone else will be on here to give you other things to test.
Good luck.