You did not state what device you are using. If it is a RPi you can copy /boot/cmdline.txt.pacsave to cmdline.txt but it would be better instead to rename the ROOT partition to ROOT_MNJRO and will never have to deal with it again with future kernel upgrades.
The newer partitions have changed names from BOOT / ROOT to BOOT_MNJRO / ROOT_MNJRO in the later images. Re-name only the ROOT partion as it will be defined in /boot/cmdline.txt. The BOOT should be ok as it should be defined in /etc/fstab. Yours should say this right now:
[ray@pi4 ~]$ cat /etc/fstab
# Static information about the filesystems.
# See fstab(5) for details.
# <file system> <dir> <type> <options> <dump> <pass>
LABEL=BOOT /boot vfat defaults 0 0
Either rename root=LABEL=ROOT_MNJRO to root=LABEL=ROOT or rename your ROOT partition to ROOT_MNJRO. The later would be best. All future kernels will replace the cmdline.txt after each upgrade to root=LABEL=ROOT_MNJRO so you will have to remember to modify it each time.
@Darksky in the end the problem was the kernel that only allow me read sd from my sd reader I had to use an USB sd reader to rename the label, after that manjaro-arm works. Thanks a lot, you save me the live two times