TIFF files not showing but TIF no problem

[calgon]

XnView 2.43 Classic set as default for all photos

Attached two files:
Tif File.tif – MD5: ce9bbc54c4700c649aa7a3957957ac56
Tiff File.tiff – MD5: ce9bbc54c4700c649aa7a3957957ac56
Both files are identical except for extension & name

When I double click either file in File Explorer:
The Tif File.tif opens & everything is correct and I get: Tif File.png
The Tiff File.tiff XnView opens but nothing is shown: Tiff File.png

If I go to file open both files open correctly.
If I drag and drop both files open correctly.

Same problem with all my TIFF files, files with extension TIF no problem.

Windows 10 x64: 1709.16299.248

What am I doing wrong or is this a bug?

[xnview]

if you put these 2 files in a folder, you can view them in XnView's browser?

[calgon]

if you put these 2 files in a folder, you can view them in XnView's browser?

Confirm can see both files in a browser folder.

It is only when I double click a tiff file that nothing shows

[xnview]

so i think that there is a problem in registry with .tiff entry

[calgon]

Thanks for your suggestion.

Problem solved by doing the following:
Uninstalled XnView
Restarted
Ran Regedit and removed all instances of XnView
Restarted
Installed XnView
Ran XnView as Admin
XnView Options/Windows File Associations
Set Xnview as default App.

Now works perfectly so as you say it was a registry problem but have no idea what caused it.

Thanks, Nick