update the BIOS / UEFI
Probably your BIOS version doesn't support the new Ryzen CPUs.
So, you have to update your BIOS with old Ryzen CPUs.
You can try several methods for this:
1) Borrow old Ryzen CPU from your friend and update BIOS.
2) Go to local service of MSI. They can update BIOS.
3) Go to your seller. Maybe they can help you.
4) Request bootkit from AMD. Here is the link: