Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
That certainly suggests a problem with Roku, however, I wasn't able to load Sling on my desktop computer either, and that's completely independent of Roku. Still waiting for a response from my ISP and Sling. I'm beginning to wonder if it's a wireless router problem but I'm reluctant to replace the router until I hear something from tech support at my ISP and Sling.
I assume you're using a wireless router. Just out of curiosity, what kind of router do you have and what's the model?
Here's an update. In addition to the support request at my ISP, about 10 days ago I also initiated a support ticket at Sling. The customer service rep that took my request said to check from time to time to see if Sling would load which I did. Communication at Sling is pretty bad: I never heard from anyone at Sling's support department. However, a few days ago, Sling suddenly started working again. I checked with my ISP; they said they hadn't done anything, so it must have been something that Sling support did. That lasted a couple of days and then a new problem: Sling loaded but the individual channels would not. Another support request and a day later everything was working again. I have no idea what Sling did to correct either problem, but it's been corrected, at least for now. So, if you have a problem with Sling not loading, call Sling at 855-729-0069. Explain the problem. You'll probably have to go through the customer service rep's scripted trouble shooting procedure. If/when that fails, ask the rep to open a support ticket. Hopefully, you'll get results as I did.
I was having a similar problem. I work from home and for one of the applications I need to use, I had to change my DNS settings to OpenDNS. I did nothing else, and miraculously, Sling TV and FreeSpeech TV (FSTV.org) started working. I don't have a good reason why; others have indicated that dynamic DHCP might be the issue, but I didn't change any DHCP settings on my router. I use a NetGear Orbi r5 series.
Hope this helps those who are still having this issue.