element not found after scroll down

After calling this code, I can see the element on the screen of my mobile phone. but earlgrey can not found the element.

`
[[EarlGrey selectElementWithMatcher:grey_allOf(grey_accessibilityID(@"tableView"), grey_kindOfClass([NSClassFromString(@"xxxx") class]), nil)]
performAction:grey_scrollInDirection(kGREYDirectionDown, 1000)];
`
`
[[EarlGrey selectElementWithMatcher:grey_accessibilityID(@"xyz")]
assertWithMatcher:grey_sufficientlyVisible()];
`

I can see from the log that element does not appear in UI hierarchy.

Please make your suggestions.