Question:
Why a System Administrator cannot use Vault Loader?
Answer:
An Administrator may not have all necessary permissions. For Vault Loader (and other similar permissions), the permission needs to be specifically assigned in order to use.
Note: System-provided permission sets cannot be modified. A user that is an admin and has the desired permission assigned needs to add this permission. A Vault Owner can do the assignment, as most permissions are associated with that account.
- Navigate to: Admin --> Users & Groups --> Permission Sets.
- Hover over the System Administrator Actions.
- Click the Action Icon (gear icon) next to System Administrator Actions, and select Make a Copy.

- Name and describe the new Permission Set as desired, and click Save.
- Click on the newly-created Permission Set.
- Click the Application tab.
- Click Edit in the upper-right corner of the screen.

- Scroll down to the Vault Owner Actions, and enable (check) the box under Vault Loader.

Related Documentation:
Vault Help Documentation: About Permission Sets
Thank you