This one is a bit of a mystery. K2600RS is not recognizing any sample RAM. I’ve bought new RAM, same thing. Not passing diagnostics. I’m at a loss as to how to address this.
Thanks.
Hope this helps. 
1) Make sure you have the correct RAM chips and they have the correct specifications needed for the Kurzweil K2600… Double check the owners manual. Also, make sure they have the correct amount of pins located on the bottom of the RAM chips. 2) Make sure to have the RAM chips seated in the slots correctly and not backwards or upside down. The pins need to face down. Make sure you wear rubber gloves whenever installing or removing the RAM to avoid static and possibly damaging the RAM chips.
3) I believe the K2600 has 4 RAM slots. If you only have 2 RAM chips installed make sure they are installed in the correct RAM slots 1 & 2 not 1 & 4 for instance. Also, If your K2600 came with RAM installed remove the 2 new RAM chips to see if the original RAM chips show up on the K2600. If they do show up, then you have to make sure the newer RAM chips are the correct compatible type. Best of luck!
Sincerely,
Mike D.
Thanks Mike.
To be clear, the RAM worked for years and suddenly stopped.
The K2600 unlike previous models handle RAM in individual slots. so I’ve tried the original RAM in individual slots as well as the new RAM I purchased. I guess for $20 I can try another set of RAM but I’m at a loss.