Thumbnails not visible in a folder that is synced with the cloud

[Duqil]

I've got a folder with files that are backed up automatically to my NAS (Network Attached Storage). So my files are stored both locally and on a separate device. Similar to OneDrive, it's called Synology Drive
With Icaros installed, all my files show thumbnails in the Windows Explorer EXCEPT for the files in THAT folder and its subfolders.
Is there anything I can do about that? Is this a known issue?
I've tried with both Windows 10 and 11

[Xanashi]

I've got a folder with files that are backed up automatically to my NAS (Network Attached Storage). So my files are stored both locally and on a separate device. Similar to OneDrive, it's called Synology Drive
With Icaros installed, all my files show thumbnails in the Windows Explorer EXCEPT for the files in THAT folder and its subfolders.
Is there anything I can do about that? Is this a known issue?
I've tried with both Windows 10 and 11

Hi Duqil,

Most network/cloud based services on Windows (NAS, OneDrive, Google Drive etc.) has their own thumbnail providers, generating the thumbnails via the cloud software.

This means that only filetypes that are currently supported by that service will get thumbnails before they are downloaded and stored locally on you computer. 
As soon as they are placed on your drive, the shell extensions installed on your system, such as Icaros, will take over thumbnailing and property generation.

In the past I've noticed that Windows sometimes allow local shell extensions to thumbnail the locally synced files in cloud folders (the files in your screenshot with the small checkmark),
but it seems like Microsoft has changed this behavior in the past couple of years, so it doesn't work any longer. I assume it has something to do with security or it could be a bug.

You could try other softwares like RaiDrive and see if that makes a difference when you access your network/cloud files.