Thinking about how to let users use a web service

I'm developing a service, Mover(What is Mover? =>  https://www.linkedin.com/pulse/mover-im-developing-new-service-tomoharu-tsutsumi/?trackingId=gPerVvD%2FwizfYuMo2C0J3A%3D%3D)

I've understood how to increase the number of users in my service, but the next issue has occurred. It is that users don't use Mover. They registered, however, they didn't login again at all. I have to iron it out.

If you face this issue, do you want to contemplate hypotheses? Maybe, it is not correct. All you have to do is talk with your customers. Of course, when I recognized this issue for the first time, I tried to think about why they didn't use Mover without talking with users. It was a mistake, it is important to communicate directly with customers. How? It is easy. What you have to do is to have a contact with users through Twitter, and email. I composed sentences to ask users for the bad points and good ones of my service. After taking the questionnaire, I'm going to think about the next strategy.