When the simulation time shown is 0 then the problem is typically initial conditions to avoid an initial 0/0
When the simulation time is very small like eps or 1e-13 but non-zero then variable step size is typically involved and typically either initial conditions are at fault or the blocks are not wired right
If the simulation time is a bit larger and equal to the fixed step size then a fixed size solver is in use and initial conditions are at fault or the blocks are not wired right.
If the simulation time is a very small number of steps, no more than step time multiplied by number of derivatives, then initial conditions or blocks not wired right.
Otherwise, your system is unstable. Possibly different initial conditions would allow it to escape the unstable zone but more often your equations or parameters are wrong.
In your particular situation that simulation time does not appear fixed step or initial steps to me. I think your system is unstable, at least for those initial conditions.
