I forget my The things gateway ID

Hi guys
I want to add in V3 a gateway The Things Gateway i have used in the past under V2 of The Things Network.
I have deleted this gateway from V2 and i have added this gateway in V3. After configuring the gateway in AP the third led is blinking fast meaning activating, but it stays in that statement even after 24 h and a reset and switch off gateway + switch on don’t give any change…Any Idea???
By the way i get another the things gateway for which i don’t remember the id…Do you have an idea to retrieve this id or to factory reset the gateway The Things Gateway: i didn’t found anything on web about that possibility of total reset to be able to give a new ID for my gateway.
Thanks a lot for your answers.