You have twothree options:
Either lowerLower your browser's zoom level (I had to reduce it to 90% because I had Hide left navigation disabled in profile Settings).
Or enableEnable Hide left navigation in your profile Settings so you can see the graph at 100% zoom.
Use a monitor that has a higher resolution.
It seems the behavior has changed a bit since the issue was first mentioned inSource: The reputation graph disappears when zooming in past 100%.