Pro Tools Express won't work in OS X 10.10.2 Yosemite

I purchased Pro Tools Express on December 25, 2014, now I am finally trying to use it and I am unable because when I try to install it, a window pops up that says "Pro Tools cannot be installed because the following error(s) were found on your system:

- An incompatible version of the OS was found. Pro Tools 10.3.4 requires Mac OS X version 10.7 or higher." I have a MacBook Air and it's OS X YOSEMITE 10.10.2 which is the latest version, I do not understand how to fix this.