ResurrectorRTX

I'd say there's an incompatibility between your old and new sticks even if they're running at the same speed with the same timing settings. Try and set your settings manually as c-attack mentioned above. If that doesn't help, I'd suggest returning the new sticks and buy a new 4x8GB or a 2x16GB kit. That way you can be assured that the sticks will be working together as intended.

I would suggest returning the kit and request a new one, sounds like a defective kit. Does your debug LED on the mainboard show any codes to work with during POST?

Yep, don't mix different kits with each other. Try and return your recently bought kit and buy a fully new one with desired memory capacity and sell the old kit.

I also had a similar issue with the RGB lighting. When booting up my PC, one of my RAM sticks wouldn't light up but all the other three worked perfectly. The problem was that MSI's Dragon Center was also controlling my RAM RGB lighting with Mystic Light. I didn't delete it though but deactivated the function for overriding third party RGB software which was active for some reason and probably created a conflict with iCUE. Looks like it fixed the problem in my case.