I am trying to download GRETL for MacOS with Intel Processor.

I follow all the proceedings and suggestions given but any time I try to download it, it tells me ''The installation Failed" and to contact the software manufacturer. 

There's still capacity to support the installation of Gretl on the disk. 

I tried to figure out why but I can't understand. 

I got a Macbook Pro 2017 version 13.2.1, I would be glad if any of you may help me. 

Thank you again, best regards