MusicMagpie revised offer

Hi,sent a Apple iPad pro 2018 WiFi 64GB to MusicMagpie in pristine condition to sell and quoted £390 which was £360+£30 bonus with offer on the website and I put the iPad back to factory settings and checked before I sent it with it starting up to the welcome screen and you select your language you want anyway just received an email and to my horror the wrote they have checked the tablet and it won't turn on and there revised offer is £36.00 so do you want to accept or decline offer and I'm shaking with anger what on earth do I do here are need some help.Thanks. PS I never took a video packing the iPad which I presume I should off