Microsoft damaged the file association in the latest Windows 10 April 2018 Update (KB4462919). Howtogeek resources found that some applications cannot be installed by default for certain file types.
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According to testing, applications such as Photoshop and Notepad ++ cannot be installed as applications by default in Windows 10. The new update only affects a number of third party applications, because other applications such as VLC can be installed by default for video files.
More details can be found. here.