Why did all my coins change to TU7 after recovery

I logged into my wallet from a new device and suddenly got a transfer notification. I’ve had this twice. After the recovery, my entire balance was reset and turned into a coin called tu7, which I could never use. Can you tell me why I am experiencing such a thing? I want to know why you convert all my coins to zero balance and convert it to tu7 when I log in on a new device.