You're definitely on track with that troubleshooting! Another thing you might try is updating the Roku's connection to the Internet, as is mentioned in the article linked below:
The Sling Moderation Team
P.S. You may have to wait five minutes or so after updating the Roku's connection before the icon for Roku streaming appears in SlingPlayer for your mobile device.
I'm having the same issue. the icon to throw the stream to the roku has disappered permenantly. i've tried everything in the faq and then some including resetting the roku to factory settings and totally refreshing everything, uninstalling and re-installing the app on my phone, even restoring my iPhone from a backup. any other suggestions?
Response to Brokenyolk.
I cracked it in the end after returning two Roku 3's to the store, thinking they were faulty.
The Roku always worked on installation then stopped showing the icon when subsequently used.
I found that after installation and the first time use if I rebooted the iPhone everything was fine after then. But be aware the icon does not come up immediately, it can take upto and beyond five minutes. Roku is fantastic technology and great to use after you understand what you have to do.
Sent from my iPad
I won't list the 20 things that I tried to get the icon to come back up over the last two weeks.
I did finally get it to re-appear yesterday by toggling the quality setting from Auto to High Quality. Don't know if it actually was the answer as I also installed a new Roku on another TV.
I agree that my Slingbox is the bomb but do wish that the Roku app wasn't so d*mn buggy. Was hoping to ditch my WDTV, which has a built in Slingplayer because the latency drives me crazy, but going to have to keep it hooked up in case the icon decides to go on vacation again.