Adobe Flash CC 2015

I'm having lag and memory issues with the latest versions of Animate, so tried to use my 2015 version of Flash as it has been so dependable (and the newer brush is so laggy).

But now I can't open it? Our team is working on updating assets for our online game so I kinda need 2015 to work again. I have been a paying Flash customer for a while now and would really appreciate it if I could just get a 2015 version of Flash to work again.