This means that the monitor cannot synchronize with the signal that it is receiving from the computer. See Monitor Specifications for the horizontal and vertical frequency ranges addressable by this monitor. Recommended mode is 1280 x 1024 (for E1713S) or 1600 x 900 (for E2013H) or 1920 x 1080 (for E2213H/E2313H).
You will see the following message before the DDC/CI function is disabled.
When the monitor enters the Power Save mode, the following message appears: