When you install Windows using a Legacy Device is marks the Boot Volume with an Master Boot Record (MBR) label

I use easybcd to load all my ISO’s on a single USB which doesn’t support UEFI 

You need GUID Partition Table (GPT) for UEFI Boot

You can check this via Disk Management

Restart the PC into Safemode with Command Prompt ( Or Hold down Shift when you click on Restart on the login screen )   

*You will need Local Admin password for this!

Run this command to make sure the drive can support GPT 

mbr2gpt /validate

Then Run this 

mbr2gpt /convert

After this you need to change the Boot Loader to use UEFI instead of Legacy

To do this with a System with Bitlocker

Suspend Bitlocker before hand then reboot in command prompt