See possible reasons below
- Battery drainage
Remove the battery for at least 1 minute, plug to charger without the battery, press and hold the power button for 20 seconds, put the battery back while phone plugged to a charger, let it charge for 5 minutes.
- Dirty battery contacts
Clean the contacts on both the battery and phone using clean dry soft cloth
- Corrupted firmware
Reloading the firmware is required' See how here http://www.satechhelp.co.za/10361/Download-Flash-Rom-Firmware-Mobicel-Retro