Mercedes: key, 2003 clk 320, memory board

Question
Hello,
I have a 2003 clk 320 and key won't turn ignition or lock or unlock doors the loghts and electronics wrk radio etc, but when you put key in ignition it won't turn I have replaced batteries and still nothing, when replacing batteries heard something ratteling so had the memory board removed aand small piece resodered and put back still nothing, recharged battery because dead from sitting I think I have tried everything . Help any suggestions?

Answer
If this is a Mercedes security key, then you may have to have the dealer recode the key. or replace it.
I had to replace my key on my 1986 420SEL it was 50.00 and I had to show up in person with photo ID and the title to the vehicle before they would take my money.
I here that some of the later model keys are 200 ot 300  dollars.

Take $$$$$.