Unfortunately, we do not have a way to reboot the Slingbox 500 remotely. I understand you might of had an interruption with your internet services. At this point, it is required for you to be physically be home in order to reset/reboot your Slingbox 500.
Here is a helpful link on how to reset Slingbox 500.
If you have any further questions feel free to reply back to this forum thread.
Sling Media Support