Select from server doesn’t work – error 404

Hello,
I am using the free version and I have also wrote several weeks ago in the WordPress Plugin Support. I had one answer and then nothing. The problem is not solved and I need to.

I use WPDM from quite some time (2/3 years) and I love it, but with the last update something went wrong.
The scenario is this:
1) I upload several files from my pc to the server
2) I check if the file is present via Asset Manager, it works.
3) I create a new download
4) I click “Select from Server” and after a while, a page returns and says “Yay! 404 Not Found
Sorry, but you are looking for something that isn’t here or it’s been moved. Try a search?”

So… I can’t select the files to attach via “Select from server” and it would be great if it could work again.
I tried changing the root directory path, with the / at the end, without it, and so on… but nothing change.

If I upload via Media Library, it works, but I don’t want to choose this way because I need to have the uploaded file arranged in sub-directories.

Can you help?
Or … do I have to buy the PRO version to resolve this issue?

Looking forward to your answer, my best regards.