When you click the File Explorer Pinned shortcut in the Taskbar, the error "This file does not have a program associated with it for performing this action" may appear. However, all other shortcuts for other applications Pinned to the Taskbar may work fine, thus implying that this is not a Shortcut (.lnk) file association problem.
Also, Unpinning the File Explorer shortcut and Pinning it again in the Taskbar may not help.
Download Folder association fix from File Association Fixes For Windows 10 (Default Settings), unzip and run the enclosed Registry File. Logoff and login back. This should fix the problem.
Press WinKey + R to bring up the Run dialog. Type the following path and press ENTER:
%AppData%\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar
In the folder that opens, delete the File Explorer shortcut.
Create a new File Explorer shortcut in that folder. To do so, right-click an empty area in the folder, and click New -> Shortcut. In the Location text box, type explorer.exe and press Next.
Name the shortcut as File Explorer. This is important, so that the existing File Explorer Taskbar Pinned item uses the newly created shortcut.
For a Windows 7 version of this article, see Fix Explorer.exe Error “This file does not have a program associated with it” in Windows 7
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Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and has a vast experience in the ITeS industry — delivering support for Microsoft's consumer products. He has been a Microsoft MVP [2003 to 2012] who contributes to various Windows support forums.