Hi,
The simple commerce module has a bug. Products that contain accents on the title are not added to the purchases.
I reported this problem in October last year:
http://ellislab.com/forums/viewthread/225182/
A bug report was created here:
https://support.ellislab.com/bugs/detail/18277
I just updated EE to version 2.6.1 - Build Date: 20130506 and the bug is still there.
Could you by any chance PM me the code to fix this?
Thank you,
Juan