Unable to import an iso image

Hi, I tried to import the official Ubuntu netboot install ISO image, found at :

http://archive.ubuntu.com/ubuntu/dists/bionic-updates/main/installer-amd...

But the Cloudmin import form reject it with this error :

"Failed to import image : Image file does not appear to be an ISO 9660 CD - format was detected as DOS/MBR boot sector, code offset 0x58+2, OEM-ID "SYSLINUX", sectors/cluster 4, reserved sectors 4, root entries 512, Media descriptor 0xf8, sectors/FAT 136, sectors/track 32, heads 64, sectors 139264 (volumes > 32 MB) , serial number 0xdeb00001, label: "Ubuntu Inst", FAT (16 bit)"

It is also unable to import the official, normal live server installer found at :

http://ubuntu.mirrors.ovh.net/ubuntu-releases/18.04.5/ubuntu-18.04.5-liv...

Error is :

"Failed to import image : Image file does not appear to be an ISO 9660 CD - format was detected as DOS/MBR boot sector; partition 2 : ID=0xef, start-CHS (0x3ff,254,63), end-CHS (0x3ff,254,63), startsector 138548, 4928 sectors"

Apparently it is unable to handle the usual iso format used by Ubuntu, and since the Cloudmin KVM image does not work anymore we are screwed, unable to install any kind of Ubuntu server :(

Any possibility to have this fixed quickly please ?