It is possible you are trying to visualize data from a folder other than a straight forward hard drive on the system. VSim relies on VisIt for visualisation and the following are known to cause problems:
On Windows machines, data inside a directory following Universal Naming Convention (UNC), e.g., \machine\directory\file, cannot be visualized using VisIt, the underlying visualization tool to VSimComposer. UNC style paths are not supported. Instead, map the UNC path to a letter drive on the machine.
If you are having difficulties updating your particle species in the visualization window, it may be due to the order in which you are adding elements to the visualization.
Particles and grids are both meshes in the visualization tool that VSim uses (VisIt), and only the latest mesh gets updated. This may be why updating the particles does not have the desired effect; the latest mesh is the grid and it is the one being updated. If you want to update particles, you can instead add the grid first and the particles second. This sequence will lead to updating the particle sizes and styles correctly.
In certain simulations, you may be plotting multiple fields and notice that certain ones advance in time while others never update past time 0.
This is due to the fact that the latter fields, as illustrated by the J field in the Magnetic Fields of Wire (Text-based setup) example simulation, are actually static fields that are never updated throughout the simulation run. Thus, when these static fields are examined in the Visualization window, only the initial field data at time 0 is displayed because that is the only data generated.