No XFi access to my XB6 after activation of an XB7 (I will return the XB7, slow speeds)

I recently upgraded to an XB7 Gateway (from a XB6). After activation and multiple resets in the last 24h, the speeds are lower than my XB6 (both on WiFi and wired). Uploads are terrible, only 5 Mb/s on the Giga Xfnity plan (vs 35-40 Mb/s on the XB6). So, I will be returning the XB7, and will keep my XB6.

The problem now: I cannot acces my XB6 with the XFi app or XFi on the web anymore; it always shows: "your gateway may be offline". I would like to have access again to my XB6 via the XFi app. Any ideas? Thank you!