Android: not receiving data while using test key

[josh-m-sharpe]

If I set io.branch.sdkTestMode to true then my app doesn't seem to receive any data when opening a link. All it receives is this:
{"referringParams":{"+clicked_branch_link":false,"+is_first_session":false}}
I've triple checked the keys I'm using, and have set the TestMode meta-data key to true. Anything else I'm missing?

Googling around a bit it seems Branch has had issues with this in the past (2017), but I didn't find anything recent.

I'm still able to develop with the live key. But being able to use the test key would be ideal.

strings.xml

<string name="branch_key">LIVE_KEY</string>
<string name="branch_test_key">TEST_KEY</string>

manifest:

<meta-data android:name="io.branch.sdk.BranchKey" android:value="@string/branch_key" />
<meta-data android:name="io.branch.sdk.BranchKey.test" android:value="@string/branch_test_key" />
<meta-data android:name="io.branch.sdk.TestMode" android:value="true" /> <!-- Set to true to use test key -->