Your 3200MHz RAM will just run slower.

No compatibility issue — it’ll just run at 2400MHz instead of 3200.

That’s how RAM works. The motherboard and CPU set the ceiling. If your board maxes out at 2400MHz, the 3200MHz kit will automatically downclock to that speed. It won’t crash, it won’t refuse to boot. It’ll just be a little embarrassed about its untapped potential.

You can try overclocking the RAM past 2400MHz (enable XMP/DOCP in BIOS), but if the board doesn’t support it, it probably won’t be stable. Not worth the hassle for most people.

If you already bought the kit, don’t sweat it. Just don’t pay extra for speed your motherboard can’t use.