The upload fails because of a missing source.
The New upload view displays a Source input field with a drop-down menu.
The Source field is marked as mandatory.
The drop-down menu is empty. Therefore, it is not possible to make any valid selection.
Since a mandatory field is left empty, the upload fails.
Either no user groups are configured in EclecticIQ Intelligence Center;
Or EclecticIQ Intelligence Center has one or more configured user groups, but the current user is not part of any existing group.
The current user needs to be part of an Intelligence Center user group to be able to upload files manually.
If there are no configured user groups:
Create a group.
Add the current user to it.
If the current user is not part of any existing group:
Add the current user to an existing group.
After you are done, proceed to manually upload the files again.