Well Microsoft Win 10 just recently did an update and I kept getting pop ups that said 'App default reset" - images, videos etc about 20 apps in all. No matter what I did could not get the apps to stay associated. Seems many reporting this issue (Windows defaulting to its own apps = monopoly) and I found this fix for now that seems to work.
http://www.winhelponline.com/blog/wi...-associations/
Peter