I am getting error WebDriverException and ‘TextField' is not visible on the screen and thus is not interactable" while passing text second time

Environment Details

Appium Desktop Version : 1.8.2
Appium Sever Version : v1.9.1
Mac OS High Sierra : 10.13.3
Xcode Version : 9.4.1
Simulator ios Version : 11.4/11.3

I have passed text to ‘textfield’ 1st time its working fine, when was passing 2nd time its not working.

MobileElement UserName2 = (MobileElement) driver.findElementByName(“user_name”);

UserName2.click(); // not working
UserName2.clear(); // not working
UserName2.sendKeys(UserName); // not working

I was getting error
org.openqa.selenium.WebDriverException: An unknown server-side error occurred while processing the command. Original error: Error Domain=com.facebook.WebDriverAgent Code=1 “The element ‘“user_name” TextField’ is not visible on the screen and thus is not interactable” UserInfo={NSLocalizedDescription=The element ‘“user_name” TextField’ is not visible on the screen and thus is not interactable}
Build info: version: ‘3.14.0’, revision: ‘aacccce0’, time: ‘2018-08-02T20:19:58.91Z’
System info: host: ‘MacBooks-MacBook-Pro-3.local’, ip: ‘fe80:0:0:0:c52:3160:dd2d:2da8%en0’, os.name: ‘Mac OS X’, os.arch: ‘x86_64’, os.version: ‘10.13.3’, java.version: ‘1.8.0_152-release’
Driver info: io.appium.java_client.ios.IOSDriver

Capabilities {app: /Users/macbookpro/Documents…, automationName: Appium, browserName: , bundleId: bundalidname, databaseEnabled: false, deviceName: iPhone 7, javascriptEnabled: true, locationContextEnabled: false, networkConnectionEnabled: false, noReset: true, platform: MAC, platformName: iOS, platformVersion: 11.4, takesScreenshot: true, udid: udid., useNewWDA: true, webStorageEnabled: false}
Session ID: Sessionid
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)

Pleas help me.