Ransomware recovery

I install the ransmware recovery app and I make a test, i rename some .txt files to .txttt

in the app interface, I see that files have been renamed but when I select them and click on “recover”, they disappear from the list but are not restored.
I was expecting to find my .txt files in the list of my files but they are still in .txttt
what did not I understand?

Thanks for your help