Check M&M account on your PC, from Lufthansa page and from M&M page. I found out in the past that the M&M App doesn't show all segments, and other transactions are missing too. It happened to me many times, and I went mad. However if you keep trace of your actual miles, the numbers woud be correct. The agents kept telling me on the phone those flights were credited but I could't see them. After I sent them several screen shots they still kept saying the same. Then I logged into my account thrugh lufthansa.com - your miles and more account, and there they were. Everything sorted out!