Games! Yeeeah

Three possible reasons:

1. Bad DS Lite

2. Bad microSD card

3. Bad R4 Cartridge

To eliminate number one. Try the working R4 cartridge in both DS Lites. If it works fine in both, then the problem is not the DS Lite. If the working R4 only works in one DS Lite, then it could be a bad DS Lite.

If you find you have two good working DS LItes, time to check the MicroSD card. Using the same DS Lite and the working R4 cartridge, try both microSD cards in the working R4 cartridge. If both microSD cards work, then the problem lies with the other R4 cartridge and you should get it replaced. If only one of the microSD cards work, then the problem lies with the microSD card. You can try reformatting it. If that does not solve the problem, please replace the microSD card with a new one. Brands do make a difference and the Kingston brand is reputed to be the best and most reliable.