As I said "This is an interesting issue"
The disk schema is UEFI/GPT, but the firmware is BIOS (InsydeH20 Rev 3.7, with BIOS) - a hybrid setup that made me ask a lot of questions. I initially thought the machine was UEFI, based on the disk schema. The Diskpart information Don provided helped a lot. The PartWiz information might have confused some things - PW reports things a little differently than Disk Mgmnt or Diskpart.
Note that the Diskpart (the definitive source) output shows no part as active.
Can you set a GPT partition as active - yes, but it must be of type basic. It is only a flag that says this is where the system file might be and is not required for UEFI firmware to boot.
Anyway, I learned a bit and other things were confirmed - thanks Don, NavyLCDR and topgundcpOn basic disks, marks the partition with focus as active.
This informs the basic input/output system (BIOS) or Extensible Firmware Interface (EFI) that the partition or volume is a valid system partition
or system volume.
Only partitions can be marked as "active."
DiskPart verifies that only the partition is capable of containing an operating system's startup files. DiskPart does not check the contents of the partition. If you mark a partition as "active" and it does not contain the operating system's startup files, your computer might not start.