Can't return Flex box, agents giving incorrect information

I have been trying to return an Xfinity Flex box that I no longer can have, since I am moving and took the opportunity to change plans from one that had included it as a "freebie" to one that does not have it. HOWEVER, the Flex does not show up in my device list when I go to the address https://customer.xfinity.com/devices/returns, per instructions online and in chats I have had. ONLY my modem is listed, which isn't what I need to return.

I communicated with a chat agent on Saturday who said that it appeared to be an issue on Xfinity's backend that was causing the Flex to not show up; she correctly found, on her end, the exact serial number of the Flex that I had. It was just my end that couldn't see it. I took screenshots of our conversation, and she said "Sure, I am escalating this issue to our backend team and they will check your account details and will get back to you within next 2 hours. Further, you are currently logged in using the correct account details." So I thought the issue had been escalated, but I never heard back from Xfinity on the phone number they have on file, or in any other regard. I also asked, "I don't know what you have access to on your end, but is it possible for you to process the
return/print a UPS label for the Flex on your end and circumvent my end's issues seeing the devices?" And she said, "Sure, I am forwarding your details to our account management team and they will share with you a UPS label for your Flex device on your email address." But I haven't received any emails or heard anything else. I still can't see the device or start a return on it. I have tried different browsers, reloading, etc.

I followed up using Xfinity chat this evening, and this agent said he saw no record of anything being forwarded or any notes on my account, so I don't know what happened. His only suggestion was that I drive ~40 minutes to the nearest Xfinity store and deal with things there, which really isn't a viable option for me--my distance from stores means that I am counting on being able to mail my devices back, given that as an option. How do I get this issue escalated and resolved in the way that the first agent had said was going to happen? All I want is to have a UPS label for the Flex's serial number emailed to me so that I can get this resolved, as I only have ten days to do so that started Saturday the 15th.