How do I get video thumbnails on Ubuntu 18.04.1 LTS?

Video thumbnails simply stopped showing. I still get the PDFs and images thumbnails, but the video ones are no longer showing.

I've already tried everything I found in Google, but nothing works.

Could anyone help me with this?

Here's what I've already tried from what I could get in other topics/forums:

sudo apt install ffmpegthumbnailer
sudo apt install gstreamer1.0-libav
sudo apt-get install gstreamer1.0-plugins-ugly
sudo apt-get install gstreamer1.0-plugins-bad
rm -r ~/.cache/thumbnails

Then I restarted the pc.

I also tried:

sudo chown -R $USER:$USER ~/.thumbnails
sudo chown -R $USER:$USER ~/.cache/thumbnails
sudo rm -rf ~/.thumbnails/* ~/.cache/thumbnails/*

Restarted PC.

That's all the help I could find, but it's still not working.

I had a similar issue. There is an article on Hectic Geek about how to set ffmpegthumbnailer as the default thumbnail viewer for video. It's not enough to install the package. However, you don't need to overwrite the totem.thumbnailer file either, just edit the TryExec and Exec lines (sudo -H gedit /usr/share/thumbnailers/totem.thumbnailer):

TryExec=/usr/bin/ffmpegthumbnailer
Exec=/usr/bin/ffmpegthumbnailer -s %s -i %i -o %o -c png -f

Leave the rest of the file as-is. After this, you may need to close your file browser and delete the thumbnail cache for it to take effect.

Sorry for my English go to preview home folder, Edit-> Preferences-> Preview then make it Always under show thumbnails than only for file smaller than make it at lest 16BB Done.