ok i think i got ur solution. Idk how to adjust msi bioses, so if it is something simular to that im gonna tell u now do it. Go on bios, in the cpu setting and set ur Advanced clock calibiration to Auto. IF u can't find it install Amd Overdrive and i will tell u the instruction, give me a quick reply so I can help u before I go.
Go on preference tab and mark the advanced mode in perfomance controle mode and apply. After that go in Perfomance tab and click the clock/voltage. There u will see Advanced clock calibration. (Default is disabled) Change it to Auto, if that doesn't effect change to All Cores. I hope this helps . if u dont understand how to do this 100% i could send pictures Dont forget to restart after the setting!
I tried to Google to find any others who has this or had this problem. But no one has. By the way, have you checked the task manager. I recommend i to crosscheck it. Right click on ur desktop bar and choose task manager, then go to perfomance. If it show 4 windows, all your cores will be running. If not, then i cant help you more sorry