Can't install the free version

I normally make social media content featuring Manager.io but I usually get feedback that they can’t install the software. According to them, after opening the installer, their computer asks and looks for a program to open the app.

Is this something you have encountered? What are the possible causes of this?

Where did they download Manager from?

Did they download the version corresponding to their operating system and hardware?

I’m not sure about this. I’ll try to ask them first. thanks for this one.