pro tools express

Hi

I have problem... I have Pro tools express and not allowed to install it on my mac

recives the message that my pro tools which is 10.3.3 occupational requires Mac OS X 10.7 conversion or higher

so  in general I have a version of OS X El Capitan 10.11.3

i can not install the program why ?

if someone can help me install my pro tools

please...