Is my new AIO cooler mounted incorrectly? CPU temps spiking!

Just installed a new 240mm AIO on my Ryzen 7 5800X, and idle temps are hovering near 60C, jumping to 90C under light load. I've reapplied thermal paste twice and double-checked the pump headers. Could it be poor contact, or am I missing something crucial in the mounting process? Really need some immediate advice here before I damage something!