Sometime, calculation or file writing operation on FEM workbench failes. In those case, FreeCAD may not have found an executable file for simulation.
In calculation, FreeCAD searches CalculiX and start it. CalculiX should be installed on installation of FreeCAD, but if FreeCAD could not found it, FreeCAD may stop and show message like "Check dependencies...". In this case, check settings with following steps.
Make sure that ccx exists in FreeCAD installing position's "bin" directory ("C:\Program Files\FreeCAD 0.19\bin\ccx.exe" on Windows).
After switching workbench to FEM workbench, select [Edit]-[Preferences...] menu to open Preferences dialog.
Select "FEM" from icons on left side of the dialog.
Select "CalculiX" tab on a panel on right side of the dialog and uncheck "Search in known binary directories" in "CalculiX binary". Then set ccx path ("C:\Program Files\FreeCAD 0.19\bin\ccx.exe" on Windows) to "ccx binary path".
Click
button to close Preferences dialog.After checking these settings, restart FreeCAD and check whether the problem is improved on the FEM workbench.