Asus Z390-F not running 64GB of Corsair

[RayVM]

Have been running 2x16GB Corsair Vengeance Pro on my Asus Z390-F with no problems for the last 5 months, been a great build so far. But with current work loads I've bought another of the same RAM. Problem is, I can only get 3 sticks to run - 48GB, doesn't matter which order they're in in terms of slots, it sees them no problem. When they all didn't run first time, I tried one at a time, when through the whole test and got up to 3 sticks working in either slots. Any ideas what could be preventing all 4 from working? Fairly sure I've ruled out a faulty slot or stick of RAM. Even tinkered with the MemOK switch, no luck either way.

 

[RayVM]

The CPU is fine, slots all work every time I test them with ram installed in various ways. All ram work every time as well, they just won't play well together when all four are installed in their pairs. I am going to look at their voltages next and see how far I get with that.....

 

[RayVM]

It's a i9 9900k. Been told the issue is more likely the kit, basically as they are not a 4x16 kit. The first pair were Samsung hardware, the second are Hynix too. Same part number, new ones have a higher revision number. Possible?

 

[RayVM]

Sorry, should have mentioned it. Never had that issue before with any previous builds although I rarely added more ram. They are 3200 so run at 2333 from what I can see. The whole rig is geared up for serious overclocking but I haven't done that yet. Was hoping to do that once I got the 64gb of ram running. Is it maybe worth biting the bullet and buying a bigger kit?

 

[RayVM]

You know, you are probably right. That's literally what I've just been reading when looking around for other kits. I do a lot of archviz and video work and fancied a decent boost, but would there be anything you'd recommend?