1. Suspend Bitlocker protection
2. Start CMD with admin privileges
3. in CMD window run mbr2gpt tool to validate the disk
mbr2gpt /validate /disk:0 /allowFullOS
4. In CMD windows run mbr2gpt tool to convert the disk from Master Boot Record (MBR) to GUID Partition Table (GPT) without modifying or deleting data on the disk.
mbr2gpt /convert /disk:0 /allowFullOS