Manjaro doesn't boot after USB install

I installed manjaro xfce 18.04 on a dell xps13 l322x from a USB. When the system reboot I get always the same error "Operation system not found". I tried all suggestions found:

The system start with usb, press c and
grub> search.file /etc/manjaro-release root
grub> configfile /boot/grub/grub.cfg
but no way to fix the problem.
Thanks for your help!

[piero@piero-pc ~]$ efibootmgr -v
EFI variables are not supported on this system.
[piero@piero-pc ~]$ sudo parted -l
[sudo] password di piero:
Modello: ATA SAMSUNG SSD SM84 (scsi)
Disco /dev/sda: 256GB
Dimensione del settore (logica/fisica): 512B/512B
Tabella delle partizioni: msdos
Flag del disco:

Numero Inizio Fine Dimensione Tipo File system Flag
1 1049kB 256GB 256GB primary ext4

[piero@piero-pc ~]$ sudo blkid
/dev/sda1: UUID="24b9672c-b931-4819-a090-78447ee821db" TYPE="ext4" PARTUUID="369f8b0e-01"
[piero@piero-pc ~]$ findmnt -s
/ UUID=24b9672c-b931-4819-a090-78447ee821db ext4 defaults,noatime,discard
/tmp tmpfs tmpfs defaults,noatime,mode=17
[piero@piero-pc ~]$ findmnt /boot/efi

Try manjaro-xfce-18.1.0-rc8

Or the stable version 18.0.4:

Thanks, solved enabling EFI boot in laptop setup and reinstall from USB!