There maybe an option in the bios that sets overclocking to manual off of auto. Not sure what it would be called but most likely one of the first options in the advanced or area that shows other system settings for ram and pcie, and pch etc. I dont have an msi board so not sure where or what it is called, but usually with auto turned on the multiplier and other system settings are grayed out, until its taken off of auto.
Edit: found a screenshot of the bios, it is under the OC tab, and then change overclocking from simple to advanced, and then the multiplier will be the cpu ratio i think.