Latitude 3520 upgrade RAM to 2x32 GB 2666 MHz

Hello, I have a Latitude 3520 with the default 2x8 GB 3200 MHz RAM sticks. According to the service manual, the machine accepts 2x32 GB RAM sticks but I did not realise that specifies 3200 MHz and I bought Mushkin Enhanced 2666 MHz RAM sticks (https://www.poweredbymushkin.com/Home/index.php/products2/item/130-ddr4/1867-mre4u266kkkf32gx2). When I replaced the memory, the machine was powered but did not boot to the Dell logo, so the RAM sticks don't work.

Perhaps someone else here had a similar experience? I plan to return the new RAM and try to get a 2x32 GB pair that actually works for this machine.