I have a 06 M6 and my HUD used to be visible during the day. Now you can't see the HUD during daytime but is perfectly visible during the night time.
It's not the on/off switch and I do not wear sunglasses.
The HUD actually still works during the daytime, I can still see it if i really look for it but it super faint and 99% invisible during the daytime. I tried adjusting my seat up and down to see if it's the viewing angle but it is not, as I can see it perfectly during night time.
I have also adjusted the HUD brightness to 100% and there is no difference.
could it be a fuse? Has anyone else had this issue?