The CPU Fan Speed error is common error due to the usage of the liquid cooling, and not a regular aircooled method on our systems. 

This method is a bypass to the sensor due to older systems not having an AIO Cooler header plug on the motherboard and the CPU fan header does not provide enough sustained power to keep the pump running at 100%

Enter the BIOS, switch it to Advanced Mode (you can press F7 to switch between EZ mode and Advanced mode), and navigate to the Monitor tab. 

Once on the Monitor tab, set the CPU Fan Speed from N/A (Not available) to IGNORE. Press F10 to save changes and exit.

This will disable the sensor and allow you to boot normally. If you have further questions, or need help navigating your BIOS screens, please contact the support department.