NDS games on tablet

Probably your connection isn't timely. Try making sure the signal is strong and stable. Just try again, no points will be further deducted if you re-download the same file within 48-72 hours from the time of your first attempt.

 

Then I guess it's hard to tell what could be the problem. You haven't mention much for us to deduce the issue. I guess just try again, the NDS rom aren't problematic. Unless you'd mean you failed to extract them, in which case, most newer ones are compressed using the latest WINRAR 5.0 or newer. If failed to extract is the case, then get latest extractor program. Otherwise, do elaborate your issue.

 

Using emulators of cause, doesn't matter if it's apple or android OS.
There is/are for those.

 

Speaking of this; this is what comes to mind;