Attempting to port my code to collada-dom 2.4.2, I discovered that dae.open now always returns NULL.

Looking at the code, it appears the issue happens here:

domCOLLADAProxy* DAE::openCommon(const string& path, daeString buffer) {
    close(path);
    string uri = makeFullUri(path);
    plugin->setDatabase(database);
    if (plugin->read(daeURI(*this, uri.c_str()), buffer) != DAE_OK)
        return NULL;
    return getRoot(uri);
}

the return NULL in the if statement is being triggered. That appears to come from here:

daeInt daeIOPluginCommon::read(const daeURI& uri, daeString docBuffer)
{
    // Make sure topMeta has been set before proceeding
    if (topMeta == NULL)
    {
        return DAE_ERR_BACKEND_IO;
    }

*snip*

The topMeta variable should be populated by the owning DAE object at DAE::setIOPlugin on this line:

    int res = plugin->setMeta(getMeta(getDomCOLLADAID()));

The nested getDomCOLLADAID call is to this code:

daeInt getDomCOLLADAID(const char* specversion)
{
#ifdef COLLADA_DOM_SUPPORT150
    if( specversion == NULL || strcmp(specversion,"1.5.0") == 0 ) {
        return ColladaDOM150::domCOLLADA::ID();
    }
#endif
#ifdef COLLADA_DOM_SUPPORT141
    if( specversion == NULL || strcmp(specversion,"1.4.1") == 0 ) {
        return ColladaDOM141::domCOLLADA::ID();
    }
#endif
    return NULL;
}

You'll note we expect a specversion argument but have none passed, so we'll always return the version 150 ID it seems.