Sir, I have the same problem recently purchased Gigabite Z390 Mini ITX MOB and vengeance LPX 16gb. This ram is not fitting to the slot of the mob. On careful examination its notch is not matching with my older DDR 4 RAMTrying to install DDR4 2400 into H270-ITX/ac motherboard and it will not click in. Notches are lined up and I have applied more force than I should be it just won't go in. Never had an experience like this with RAM before.
Please start a NEW thread for your particular situation.Sir, I have the same problem recently purchased Gigabite Z390 Mini ITX MOB and vengeance LPX 16gb. This ram is not fitting to the slot of the mob. On careful examination its notch is not matching with my older DDR 4 RAM