I am sorry to hear that you are having this issue. I know that when things aren't working the way that they are supposed to it can get very frustrating. I have attached a link that I hope will be helpful in finding a resolution to this issue.
Hope this helps,
Sling Moderation Team
Unfortunately, that doesn't help a lot
x8007274d --> The connection attempt failed. Make sure the Slingbox you are trying to watch is on, set up for remote viewing, and not blocked by firewall or NAT settings
I pretty much try everything that can be found on this site with this error code. Like I said, nothing, nothing as change from my configuration at home, so can it stop working? Yes, the slingbox is ON...basic stuff here.
Even connecting the cable directly from the slingbox to my router or laptop, I can't connect to it. I can't even reset it. I shut down everything (router, slingbox, modem cable, etc...), reboot and still to no avail.
So, we are stuck with a product paid over 200$ with barely any quality support.