I go to Win-I > Apps > Default Apps. It says my video player is set to MPC-HC. If I use Windows File Manager to open the folder containing the .wmv file, the MPC-HC icon appears next to it; and if I double-click on the .wmv file in that folder, the .wmv video plays. Win-I > Apps > Default Apps > Choose Default Apps by File Type confirms that MPC-HC is the default player for .wmv files. This is also the situation for .mp4 files. It is not the situation for .flv or .mpg files.This file does not have an app associated with it for performing this action. Please install an app or, if one is already installed, create an association in the Default Apps Settings page.
This is a new problem; I have been using these programs for years without this problem. Possibly the upgrade to 1809 is responsible, but I don't seem to be getting this problem with other filetypes, though I haven't yet checked them all.