As you’re on a different broadband network BT Support can’t access to the router.
@sasghar12345 I bought my SH2 router on eBay to replace a SH1 router. I wanted to put in the BT Disc to extend Wi-fi into my garden but keep the same SSID.
As I have BT broadband BT updated the firmware.
So you have a few options: give/loan to a friend on BT Internet or sell on eBay with advice it needs to be used on BT Broadband.