I recently purchased a new RAM module for my new 2020 iMac. I went with this model from Crucial since it seemed to fit the specifications from Apple's website: https://www.crucial.com/memory/eol_ddr4/ct16g4sfs8266
However, when I received it and put it in my iMac, it fails to boot. I've tried it in every slot in multiple configurations, when this module is in the computer, it won't boot. I'm aware of the memory initialisation process, so have been waiting longer than 30 seconds before powering off.
After doing some Googling, I came across this model from Crucial on Amazon that many people report working on their iMac: https://www.crucial.com/memory/ddr4/ct16g4sfd8266. For clarity, mine is the ct16g4sfs8266 and this is the ct16g4sfd8266. One character difference!
Other than the model I purchased being EOL, the specs for these two modules on Crucial's website seem to be identical. They are both DDR4-2666 SODIMM memory, so I'm failing to see what might be causing the module I bought to prevent boot. Does anyone have any experience with either of these modules? Did I just get unlucky and get a bad module?