Thumbnail display not showing

[HerrBill]

On opening, XnView no longer displays thumbnails in the thumbnail pane. Any suggestions as to how I can switch it back on again.

[xnview]

could you post a screenshot?

[HerrBill]

Screenshot as requested

[XnTriq]

What are your settings for View → Filter by, Bill?
The preferences for View → Filter by → Custom are configured in Tools → Settings… → File list → Custom filter.

[HerrBill]

Under custom filter, all boxes are ticked with the exception of video which is listed under the heading 'show as thumbnail'. I ticked this box but it had no visible effect.

[xnview]

if you use Filter by>Image, same thing?

[HerrBill]

Filter by image has done the trick. Thanks for your assistance.
Question 1, any idea how this option might have been switched off?
And 2, is there a quick, self help reference available that beginners/ newbies to XnView such as I, could refer to in time of need?

[xnview]

you have perhaps clicked on the icon

[HerrBill]

thanks