How do I reload my thumbnails after deleting them for space? GOOGLE PIXEL 2

[Android Central Question]

I deleted my thumbnails to free up space as I was running low. Now I have thousands of pictures with no thumbnails and so when I try to send them through something like Instagram Direct Messages, I can't see which image I'm sending.

 

[Rukbat]

Back up all the pictures. Delete them all. Restart the phone. Copy the pictures back. Restart the phone. That should recreate the thumbnails.