First, we recommend you to check if the TV source attached to your Slingbox is a supported device.
If it is, we recommend you to uninstall and reinstall the SlingPlayer Mobile application on your Mobile device.
Make sure to follow these steps and let us know how it works.
As you say that everything is fine with Slingplayer for PC the problem must lie in the Android player. I have seen dozens of postings over the last few months with people reporting odd behaviour with the Android player so I suggest you do a search on the forum for "Android" and see if a solution has been offered.