Sorry but the source code I pasted here doesn’t work fine, I rewrite it from scratch and now works like a lightning storm 
In my case, the wait.Until sentence doesn’t detect the element I was looking for and when the timeout is reached it exits without throwing an exception
The new code makes the job in only 2.8seconds (the time that the APP gets open):
in C#:
while (miCrono.ElapsedMilliseconds < configuracion.script_TimeOut)
{
try
{
AppiumWebElement item;
item = configuracion.appium_Driver.FindElementByXPath("xpath_of_the_element");
if (item != null) break;
}
catch (Exception ex) { throw new Exception("2"); }
}