My problem is that every time I need Adobe Digital edition I have to reinstall it all the time, when I open it it says installer package??? Please help thanks celine

I have a Mac and my friend has a PC and no problem, it seems that this happens only with the Mac, I download adobe digital edition and it works for once but if I need it again I have to reinstall it that's why I don't understand, I am french and have trouble explaining my problem.

If someone would explain I would really appreciate, it gives me ADE 4.0 a red circle and when I click on it it says digital installer package, I do install it but as I said every time I use it I have to reinstall it???

thanks for helping

céline