Answer to: New RAM not responding.The problem is that you have the wrong replacement RAM module. RAM requires that you match the specs very precisely. You can find the existing RAM specs in System Profiler, or by running the following terminal command: system_profiler SPMemoryDataType Match the speed (MHz), and whether or not it uses parity bits (ECC). You can also look up the maximum defined memory that the system can reliably use. It's not going to be a given that you can install 16 GB. If memory serves, that model can accept 8GB without trouble.