I created a loop device with

$ truncate -s 20G test.img
$ losetup -fP ./test.img
$ losetup -a
/dev/loop0: [0032]:4051 (/tmp/test/test.img)

lsblk is able to see it just fine

$ test]# lsblk 
NAME        MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTS
loop0         7:0    0    20G  0 loop
...

Now I'd like to create partitions with parted on that device, however, parted is unable to detect /dev/loop0

$ parted -l
Model: SAMSUNG MZVLB512HAJQ-000L7 (nvme)
Disk /dev/nvme0n1: 512GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End    Size   File system  Name     Flags
 1      1049kB  538MB  537MB  fat32        EFI      boot, esp
 2      538MB   512GB  512GB               primary

Why is parted not detecting the loop device?

Updated

$ partprobe -s
Warning: Unable to open /dev/sdb read-write (Read-only file system).
/dev/nvme0n1: gpt partitions 1 2