How to repair Puzzle marked as ??? in Puzzle Swap?

Solution 1:

Ok, I gave up on the puzzles (my heart bleeds) and started it anew. After a day I got via SpotPass the first puzzle with red tiles, and later the Kid Icarus-Puzzle. This time it didn't broke, it was all available in StreetPass-encounters. Only I had to start fresh. :-(

I don't know, why it was broken in the first place, maybe some error while writing the flash-memory.

Solution 2:

Since I don't see the correct answer here I suppose I'll revive this question...

Certain puzzles are only available in certain regions. If someone you streetpass has a puzzle that is not available to your 3DS's region, it will show as a blank puzzle labelled "???".

For information about which puzzles are available in which regions, see http://nintendo.wikia.com/wiki/Puzzle_Swap.