Another issue with Windows 10 rears its head. HowToGeek reports a recent update seems to have broken file associations. The site tested the issue on multiple Windows 10 PCs and confirms they all had this problem. The bug is pretty weird though, as it does not affect all programs:
This is a strange bug. It affects some applications, but not others. For example, Windows 10 won’t let you make Adobe Photoshop or Notepad++ a default application for images or text files. But you can make other applications, like IrfanView, VLC, or Google Chrome, your defaults.
HowToGeek speculates the issue was introduced by KB4462919, an update that got rolled out on October 9.
Interestingly, the bug seems to be fixed in Windows 10 October 2018 Update, but that update got pulled due to issues with data deletion. At the moment, it's still unknown when Microsoft will re-release October 2018 Update.