There are a few possible reasons for this, and here are some links to the troubleshooting page along with explanations:
1. [[Dell Inspiron M5030 Troubleshooting#Section_Broken_charging_port|Your charging port may be broken.]] This is most likely the case if your port looks damaged.
2. [[Dell Inspiron M5030 Troubleshooting#Section_Motherboard_error|Your motherboard might have an error.]] Most likely, if this is the case, you won't be able to use your computer when it's plugged in, either.
3. [[Dell Inspiron M5030 Troubleshooting#Section_Broken_battery|Your battery might be broken.]] If your computer works fine on the charger, but the battery won't hold a charge, this is probably the case.
Hope this helps!