This may be because the batteries are running low, remove them and plug in the mains adapter. The Solo can be run off batteries for short periods of time but is designed to run off the mains adapter provided.
You should also check the time set on the display, access the basic settings by holding the middle button down. If the display time is incorrect you can edit with the left and right buttons and confirm with the middle button.
The last thing to check in the settings is "pwr.dwn" this is a sleep mode, which will turn off the screen after short time. If set to OFF the display will stay on.