I found a solution to the same error message:
I stumbled upon "Migrate OS To SSD Troubleshooting" -
https://kb.paragon-software.com/article/94 - which explained that you have to ensure that the restore target drive has the same partition table type as the backed up drive - in terms of either MBR or GPT. My backup was from a modern GPT SSD but I was trying to restore it to an MBR-formatted USB-stick. So I had to change the USB-stick to GPT.
I use the free Paragon Hard Disk Manager 16 Basic, where you have to pay for that functionality, so instead I used GPartEd.org to convert the USB-memory from MBR to GPT. But to boot on the gparted CD, I needed to Disable Secure Boot in the BIOS... life is getting cumbersome, with UEFI, secure boot, GPT etc.etc.
But why did Paragon give me that non-sense error message "disk is not initialized"?
What annoyed me the most about Paragon Hard Disk Manager 16 Basic is, that when I wanted to put it on a boot CD, it asked me to install "WAIK ADK" from Microsoft, which takes up 7 GB on my SSD...! So I had to remove it again afterwards.
Another annoyance is that it is quite hard to figure out how far in the backup or restore process Paragon is. One minute it says 12 minutes left, the next minute the process has completed.