Error: Expo validation using react-native-form-validation

This is react expo project and the error appeared when using react-native-form-validation for validation.

value={fullName}
label="Full Name"
captionTextStyle={styles.captionTextStyle}
caption={errors.fullName.length > 0 && errors.fullName}
status={errors.fullName.length > 0 ? "danger" : ""}
onChangeText={value => this.handleChange("fullName", value)}
/>
This is one part of validation Input using react-native-ui-kitten.

The error runs because all the texts in input like labels and inputting texts.

I didn't find the reason why this error happened.

"""Error:
10:03
fontFamily "$text-font-family" is not a system font and has not been loaded through Font.loadAsync.

• If you intended to use a system font, make sure you typed the name correctly and that it is supported by your device operating system.

• If this is a custom font, be sure to load it with Font.loadAsync.
  """

This is urgent problem... please help me. Thanks.