File download not working (it's downloading TXT blank file)

Hi there,
I have a little problem,
Using CoursePress I can add a downloadable file to the students, in this case I have a PDF file pointed correctly to a file on the server but when I try to download in the course I get another path that leads me to a blank TXT file, that happened with all downloadable files.

Check attached images for details.

* Detail, I recently changed hosting provider from GoDaddy to SiteGround, although I have checked the file on the server and its on the same path, it seems OK from their part, that's why I needed to check with you guys.

that's the pdf file (working) - https://courses.nativeportuguese.co/wp-content/uploads/2015/07/Verbos_-pt25.pdf

and that's the link I'm getting when trying to download the file from the course
https://courses.nativeportuguese.co/?fdcpf=

Check attached images for details.

thanks a lot!!
Philipe