Forerunner 255, brightness settings dont work.

1. Did you do a soft reset after updating the watch?

2. Also try connect via cable to Garmin Express and do the same (soft reset and then restart)

Soft Reset - Hold in Light button until the unit shuts down completely, then restart  it after says 15 secs

Yep. Still nothing. Brightness settings not working

I contacted with the shop and it is a hardware issue. They will exchange the watch

For me there's no difference between brightness of 5% and 10% (I was setting it on the watch, and checking in a complete darkness). Does anyone else have that problem as well?

It's not a problem. It's a feature. May be on fr955 controller can 5%, 255 can't. 

If the 255 cannot handle it, then it shouldn't be available to choose. To me it seems like there's just software issue...

Garmin did actually remove 5%, but there were lots of complaints in the forums. People wanted it back. So it came back, still being the same as 10%.

I see, thank you. However, still it's rather confusing than helpful