[Kendomon]

What you can try is look for corrupt codes, certain codes input wrong can kill a gameshark device, I received a Saturn gameshark fresh from the factory and inside the it contained two sets of codes for and NFL game, one set matched a website of codes, the other was all messed up, once I removed that code grouping it worked fine.

I also had a Mini-Goldfinger, I just emptied it of all codes and input the ones I wanted and never had any trouble with it.

Then again, they could have created a bad batch and you'll need to exchange it.

A local video game store recieved a bunch of Mini-Goldfingers they were going to send back because they said they didn't work, I asked if I could look at them and I found the only problem with them was they were set to PAL instead of NTSC, all I had to do was switch them and they found out that there was nothing wrong and could sell them after all.