We have a couple articles that may help, but as I don't know the operating system or computer type, I'll give you a couple and hope one applies to your situation. Generally in this situation I recommend the user uninstall and reinstall the SlingPlayer plugin.
This article, How to uninstall the SlingPlayer plugin for Chrome for Windows shows the PC steps.
This article may also be helpful: How do I install the Watch on Slingbox.com plugin? How do I remove it?
Let me know if this helps,