At some point between v2.4.0-2016-09-21-4189 and v2.4.0-2016-10-10-4344 of tns-core-modules a strange bug has arisen.

Setting a value for padding in CSS has no effect unless a background-color is also assigned to the element.

Using the template-hello-world starter template you can reproduce as follows:

$ tns plugin remove tns-core-modules

Remove the node_modules, platforms and hooks folders.

$ tns plugin add tns-core-modules@next
$ tns run android

main-page.xml

<Page xmlns="http://schemas.nativescript.org/tns.xsd">

  <GridLayout rows="auto, auto, auto">

    <StackLayout class="test1" row="0">
      <Label text="Test 1" />
    </StackLayout>

    <StackLayout class="test2" row="1">
      <Label text="Test 2" />
    </StackLayout>

    <StackLayout class="test3" row="2">
      <Label text="Test 3" />
    </StackLayout>

  </GridLayout>

</Page>

main-page.css

Page {
    background-color: lightgreen;
}

.test1 {
    padding: 30; /* Doesn't work */
}

.test2 {
    padding: 30;  /* Does work */
    background-color: lightblue;
}

.test3 {
    margin: 30;   /* Does work */
}

Which gives the following results: