Sign out of all devices

You can try contacting Support - at one time in the past they had the ability to "reset" an account, which would log out all the devices.  It isn't clear if they still have that ability (or are aware of it), but it's worth a try.

They're not able to help. I called and spoke with 2 reps.

@bcbsncjlj Will you please stop giving this same crappy advice that you KNOW doesn't work because you have been responded to in many, many threads that your advice had no effect on this issue. Resetting the password DOES NOT WORK. Resetting the user name DOES NOT WORK. If you don't have anything useful to add to the conversation why do you keep chiming in with junk advice?

@bcbsncjlj but in the meantime, the people who are at the cabin we stayed at have access to buy ppv on our account. For months. Who knows how long? I have not needed to log back in to my smart tv at home for years. You don't know and your advice doesn't provide any solution so please stop.

That's because there really isn't a good solution to this issue. The best you can do is change your account password. Eventually those other devices will need to login again, and then they cannot. Of course, the ideal solution is to log out on any "guest" devices before you leave, but it's too late now. 

I'm in the same boat, but I am positive that I logged out of my friend's tv when I left.  The fact that it still thinks I am logged in is so incredibly frustrating. AND A HUGE FAIL ON ATT/DIRECTV's part. Why can Netflix help me but you can't??? And I am paying how much $$ for this incredibly unhelpful customer service experience?? Time to cancel people.. We can get pretty much everything we need from other providers who are much more hip to the times. 

@bcbsncjlj it was only a matter of time before your comments degenerated to rude, as I see throughout this site that they always do. Your post has been flagged as inappropriate and unhelpful. If humans were perfect, customer service wouldn't be needed, would it? In leaving the cabin, I had to make sure it was clean, per their rules, that we packed everything, the dogs were fed and walked before we got in the truck for home, etc. The last thing in my mind was the friggin TV. You have added nothing to the conversation but insults and unhelpful advice that doesn't work. JUST STOP TALKING. Are you some sort of last word freak or something? The failure is definitely on the part of the service provider. This happens frequently and AT&T should position themselves to be helpful. In fact, they previously provided the ability on the app for users to logout of all devices. Why would they remove that function in app updates? Perhaps it didn't work either. Poor functionality should be addressed and corrected. And someone should relieve you of your duties here.

@bmstanifer 

Duties? We are just customers on a public forum doing this as an act of volunteer. We are not assigned duties, nor are we required to spend a certain amount of time here every day assisting people like you. 
If you don’t like the answer given, go someplace else. 

@detuch254 When you keep repeating false advice that doesn't work, none of us appreciate it. You're wasting people's time and adding to the frustration advising things to try that you already know won't work. Wouldn't it be better to honestly state that there is currently no solution to this problem than to give people false busy work? And I see you're just as rude as your counterpart. 

@bcbsncjlj That is not true. From the AT&T website, here are the (now defunct) instructions how to get there on the app: View and manage your DIRECTV STREAM devices

Manage your DIRECTV STREAM devices. Also find out how to return your device and learn more about auto-sign in.

DETAILED STEPS

Manage DIRECTV STREAM devices

Sign in and go to your Account Overview page.

In the My streaming devices area, select Manage. From here, you can:

View a list of your devices. 

Disable auto sign-in by turning the selector Off next to “Auto sign-in.” If you have more than one DIRECTV STREAM device, this can be taken for each applicable device.

View installment plan details, if applicable.

Add more streaming devices (up to 6).

While I can understand issues with them being able to report what devices are in use - in most cases there really isn't a mechanism for them to identify specific devices or  report where a device physically is or who is using it - they have less excuse for not providing a mechanism to sign out all devices.  They should be able to (safely) do this through the account management pages - anyone who can log into those can pretty much do anything to the account anyway.  Clearly the system has the capability to flush an account and bounce all devices, so bouncing devices without flushing the account certainly should be possible (and apparently was at some point in the past).  Note that I don't think the instructions referenced about "auto sign-in" would provide any help in forcing a device to log out - they would just allow you to force it to explicitly log in the next time it happened to be logged out.

I have the same issue. Unfortunately the  only way to correct an issue such as this is to cancel your subscription and then redo it.

Except I can't because I'm grandfathered in on a plan and pricing that no longer exists.

@bmstanifer not sure if your issue ever got resolved, but I was in your same shoes and grandfathered so canceling was out of the option… or so I thought. It just so happened they “accidentally” canceled me on their end one day and then refused to give me my grandfathered plan back and boy was that an enlightening experience. I was able to get almost all the channels I needed elsewhere. It may not be what you wanted to hear (and completely ignore me if you’re on a tier with a channel that nobody else has) but the other services have come a long way and the grandfathered plans aren’t as great as they seem anymore, especially given what we’re paying for them.