AIO Pump Dead?

[MoNKeyNoPinpin]

Heyo, I was recently servicing my PC, giving it a good three month partial rebuild. While putting the loop back together my GPU AIO was working fine, but now I suspect that after finishing it all up its dead and I have no idea why or how... For context, I run an alphacool double AIO loop, both CPU and GPU have their integrated pumps and radiators in between, I am very positive that they are all in the right flow orientation (GPUout>rad>CPUin-CPUout>rad2>GPUin). Beacause of this setup I am a bit less worried as the CPU AIO pump is pretty beefy (correct if I am wrong) and my temps are ok (I have not done a prolonged stress test as I do not want to risk it). CPU - Alphacool Eisbaer Pro ES (240mm rad) and GPU - Alphacool Eiswolf 2 AIO - 360mm. Can I fix this instead of buying a new GPU AIO?