Lew Hamilton

Hello! I am very new to Mesh Lab so not the best with its interface. I have imported two point clouds from Regard 3D into Mesh Lab in order to create one object. I have aligned with point alignment but 1) it does not Process after I click Process and 2) When I then try to flatten visible layers, the entire project is gone and i have to start from the beginning. What am I doing wrong? Any help I'd be extremely grateful! Thank you!