My professor recently had a problem, and he asked me for my help to solve it, and of course I ask for yours.
He was made the School of Engineering Dean, an while it sounds important it takes most of is time through an administrative black hole, also, because of this his office is now in another building so he cannot come to the lab as often as he would like to.
He started noticing less and less people come to the lab, and some only come for a space of a couple of hours and then leave, while he perfectly understands that research can be done everywhere, he is very big on cooperation and discussion among lab members, which can't be done if there is only one guy in the lab.
Do you impose any kind of restrictions on students going to the lab for a specific time? If you are not able to monitor it, how can you ensure they will come. I was looking into some companies that have IP based checking in systems, but seems like an overkill for a 10 person laboratory.