Name locator not working in iOS app + handset


I am using appium 1.3.7 with iPhone 5s and os 7.1.1
I am using for recognising element and it was working fine and now suddenly it stopped recognising the element.
Am trying to get the value of some element like
String xxx= driver.findElement(“some name”)).getAttribute(“value”);

Earlier it was giving the correct value but now it is returning null so can anybody help me to know the exact reason?