branch.io onInitFinished is called with null object

Question

I have the following code snippet in my app. When onInitiFinished is called, on Samsung Galaxy 6, running 6.0.1, the BranchUniversalObject is passed as null. On Nexus 5, running 6.0.1, and Samsung Galaxy 5, running 5.0, the BranchUniversalObject is non-null and contains all of the info embedded in the link.

On all 3 devices, when clicking on the link, the browser starts up and then my app is started (as expected).

private void setupBranch() {
Branch branch = Branch.getInstance();
boolean branchInitOk = branch.initSession(new Branch.BranchUniversalReferralInitListener() {
    @Override
    public void onInitFinished(BranchUniversalObject branchUniversalObject, LinkProperties linkProperties, BranchError error) {
        if (error == null && branchUniversalObject != null) {
            String cannonicalIdentifier = branchUniversalObject.getCanonicalIdentifier();
            ...
        }
    }
});

}

What can I look at to debug this problem?