I've already tried a full reinstall of Dropbox & once it resynced nothing changed.

Problem is i have 400GB of files I want to have local so i'd prefer another solution that doesn't require downloading them all again if possible? If you have any issues with previews, please refer to our fix to thumbnail preview not working in Windows 10 File Explorer guide. Please make sure that the thumbnail preview is turned on in File Explorer settings. So the simple solution is to just change my master Dropbox folder to Online only & then back to Local. Open a folder containing PDF files to see thumbnail preview for PDF files.

I can then set them to Local again & then the proper files are redownloaded & the Thumbnails & search works as expected. However, just like Jinggo78's example above, if I change the folder to 'Online only' then the Thumbnails get created & they do show up in the Windows Explorer searches. These files are also not able to be searched by Windows Explorer, it seems to ignore them completely. When Dropbox is synced & unpaused they all have Green ticks, once I pause Dropbox the Green ticks change to Grey X's. Like Jinggo78, most of my files arn't showing any thumbnails.

Pdf thumbnails not showing