Qatium simulates the behavior of each network using the EPANET toolkit, which can raise some errors while it is calculating and/or finish the simulation process without returning the results for all the hours shown in the timeline.
In the hours when there are results, they will be shown in the map, in the asset details and in theme panels (pressure, flows, tank levels). But if in a selected time-step there are no available results, the graph in the asset detail will be updated and only show results in the timesteps with data.
Remember that live data graphs are available only when and where readings are available.