White light and beep for 1 second on switch on

I have an xbox Series X which my daughter took apart and gave me the motherbord to change the HDMI and returned it, she reassembled the console and plugged in the flexi from the Nexus board to to J1 incorrectly, this burnt out the flexi. I have replaced the flexi cable but now when I switch it on I get white light and bleep for 1 second. On investigating I have no V_GFXCORE and the resistance is extreemly low. On injecting 1v at V_GFXCORE nothing gets hot, when I monitor the board with a thermal camera. Not having done one of these before is V_GFXCORE normally such a low resistance almost a short about 0.5ohm.