Why curve isn't appear in XY GRAPH block?

Some times I am in trouble with SIMULINK XY GRAPH. When I run my model there is no graph or graph tails a rout like worm. Thanks

[Andreas]

Did you check the axes properties? Just double click the XY-Graph and check the settings. First (top) input is for the X-axis, the second (lower) input for Y-axis.

[Nasser Hasani]

I do,I specify right up-down limits to x and y.but i have the problem yet.