Exactly tue same problem as descrived by Jim. It works well as long as I don't take ans pictures. One picture is also ok. But it is not saved anyway. After taking a second picture, the app doesn't reply anymore.
I have the same problem using iPhone, EOS 7D II, W-E1 and CF Lexmark Professional 800x 64GB UDMA 7.
USB is not supported for iPhone, so I wanted to test wireless connection before buying the whole package. Unfortunately without success.