What Does This Error Mean?

Kobo Nightlight (ComfortLight PRO) is only available on models with a warm LED — not all Kobo e-readers have it. If your model supports it, swipe down from the top of the screen and drag the warm/cool color temperature slider to adjust the amber tint.

Affected Models

Kobo Libra 2
Kobo Sage
Kobo Elipsa 2E
Kobo Clara HD
Kobo GlowLight 3 (select models)

Common Causes

Kobo model does not have a warm LED — only premium Kobo models include ComfortLight PRO
Nightlight slider at the minimum (cool) end — does not appear to change color at this setting
Scheduled nightlight not configured correctly — auto warm light only works with a schedule set
Brightness at zero — nightlight warm tone is invisible when the frontlight is off
Firmware bug after update preventing nightlight slider from changing the LED output

How to Fix It

Check if your Kobo model supports nightlight.

Kobo ComfortLight PRO (warm/amber nightlight) is only available on select models including the Libra 2, Sage, Elipsa 2E, Clara HD, and Forma. Budget models like the Kobo Nia and older Clara 2E use a white LED only — they have brightness control but no color temperature adjustment. Check your model on kobo.com/features to confirm ComfortLight PRO is listed.
Use the color temperature slider.

Swipe down from the top edge of the Kobo screen to open the brightness panel. If your model supports ComfortLight PRO, you will see two sliders — one for brightness and one for color temperature (a sun-like icon). Drag the color slider to the right to increase the warm amber tone. The change is subtle at low brightness — increase brightness to at least 30% to see the warm light effect clearly.
Set a Nightlight schedule for automatic warm light.

Go to Kobo Settings → Reading → ComfortLight PRO → Schedule. Enable the schedule and set a start time (e.g., 9 PM) for warm light and an end time (e.g., 7 AM) for cool light. Outside the scheduled hours, the color temperature stays at your manual setting.
Increase the frontlight brightness.

The nightlight warm color is only visible when the frontlight brightness is above about 10%. If brightness is set to minimum, the screen will appear off and no color change is visible. Increase brightness to 20–40% and then adjust the color temperature slider — the amber tone should be clearly visible.
Update the Kobo firmware.

Go to Kobo Settings → Device Information → Check for Updates. Firmware updates fix ComfortLight PRO bugs introduced by previous updates on some Kobo models. After updating, restart the device and test the color temperature slider again.

When to Call a Professional

ComfortLight PRO is hardware-dependent — not all Kobo models include warm LEDs. If your model is supposed to have this feature and the slider has no effect, contact Kobo support as the warm LED hardware may have failed.