Cannot factory reset

Hi I want to sell my Fingbox as I no longer need it. I am unable to factory reset following any of the guidance I found online, chiefly this:

My Fingbox is lit green after several resets and the Fing app is consistently "discovering" the Fingbox back online a few minutes after a reset. The app or website's UI do not show me any way I can disassociate or factory reset my device.

Please help me!

Many thanks,