Hi everyone,
All nintendo DS consoles will not turn on if:
- One of the screen or their flat cables are broken or loose. (Do a visaul inspection)
- Fuses are in short circuit (You will need a multi-meter and check for continuity in F1/F2)
- Wifi card is not sitting correctly in place ( this is a very common issue even if the screens are ok).
There is plenty of information in the web, once you identify the issue get more details or let us know.
Good luck and good repair.
JM