Xbox one s wont display 4K

Hi all, I recently repaired an xbox one s with no display. I replaced the retimer chip with one from a donor board and now I have display. The only issue I have is the console won’t display in 4K. I have just bought a new HDMI cable cabable of up to 8K so eliminated the cable as the problem. I’m thinking maybe the donor chip. What do you guys think?