You already mentioned Ubuntu MATE 22.04, so the distribution itself is clear.
However, several essential details are missing:
Exact Nextcloud Desktop client version
Source of the client on Linux (Ubuntu repository, AppImage, Flatpak)
Nextcloud server version (AIO, Docker, Snap…)
Filesystem used for the sync folder (ext4, NTFS, network mount…)
Whether this started after a specific client update
On Linux, the Nextcloud client behaves differently depending on packaging and filesystem, especially with Unicode filenames. Without these details it’s not possible to determine whether this is a client regression, packaging issue, or environment-specific behavior.
Provide the missing information so the issue can be analyzed properly.
Here is the missing information, and sorry about forget to put it.
In this moment, it happens with the last version, 4.0.3, but I am having this issue since the 3.6.X if I am not wrong… At least, I can say for sure that I having this error from versions 4.0.X
I have install the clients from the Nextcloud oficial repository.
The server is at version 31.0.8, and is a standalone borebone server with a “normal” setup (I install it in the classic way, no dockers, snaps or any other tools)
The filesystem I use is ext4 in a normal install, nothing special.
As I say, I am not really sure, but I will say this is happening since versions 3.6.X. I was waiting for newest updates, because sometimes It is fixed in the following versions, but not this time.
I also forgot to mention that those files do exist on the server, but it still won’t download them, so I’ve deduced that the problem lies with the synchronization client.
One important difference here is the client packaging.
Even though you are using the official Nextcloud PPA on Ubuntu, the primary Linux distribution method is the AppImage, and behavior can differ between PPA builds and AppImage.
Please test whether the issue also occurs with the official Nextcloud Desktop AppImage.
If the AppImage works correctly while the PPA client does not, this would strongly point to a packaging-specific issue rather than a general Linux or server-side problem.
Sorry for taking so long to reply to this topic. I have continued experiencing the issue on several computers running Ubuntu MATE, and I have finally discovered something interesting:
In the latest versions of the sync app, for some reason, the sync program changes the permissions of shared folders to read-only mode (probably due to the way the share was originally created), and the program itself is then unable to create or modify its contents when changes occur.
If I change the folder permissions to 755 or 777 using sudo, synchronization works again without any problems. It is quite curious; I suppose I will have to keep modifying folder permissions on the clients whenever this issue appears.
I hope this helps.
Thank you very much.
P.S. I have checked on a Windows client and it gives me the same problem. It happens in shared folders in Nextcloud with no modification permissions (read-only). It is in these folders where the sync application makes these strange permission changes. In both cases I mentioned, I am using the latest version of the application, 4.0.6.
I can confirm that with clean system installations and the latest version of the sync program (4.0.6), when trying to sync shared folders with read-only permissions, it gives a permission denied error when creating the folder locally. When using chmod -R 755 on these folders, synchronization works correctly again.
Best regards, and thank you very much for your attention.
P.S.: I will try to explain myself better. If I create the folder “trabajo” and share it with read-only permissions, on my coworkers’ computers the “trabajo” folder is created, but it does not sync afterward, showing a permission denied error. Applying chmod on those computers fixes the problem.
As you can see with non identical locales it causes Problems with ñ in file name. As well also with german “Umlaute” äöüÄÖÜ
So i suggest to check also the locale settings on both Server and Client Computer.
For this test i used on both Client VM’s Nextcloud-4.0.6-x86_64.AppImage. So the difference was made only by locale settings. Also both client was Ubuntu-Setups. One 24.04 the other (with locale DE@euro) Ubuntu 25.10.
I will try to reorganize the topic with the new information:
Although at first I thought the permission denied sync error was caused by file names containing Ă‘ or accented characters, I have discovered that it has nothing to do with that. It happens regardless of whether the file or folder names are normal.
I believe the problem lies in how the sync client handles shared folders that have read-only permissions. For example:
2.1. User A shares a folder and its contents with User B or a group of users, assigning read-only permissions to that folder and disabling the options to create, modify, or delete. It does not matter whether this is done from the Nextcloud web interface or from their synced folder.
2.2. The clients of User B or the user group create the shared folder, but afterward they are unable to sync its contents, showing a permission denied error.
2.3. I have also discovered that if this folder was syncing correctly in previous versions that did not have this problem, and I update to the latest version (4.0.6), if a conflict appears in any file, trying to resolve it by asking the application to keep the server version does not work, and it behaves as if it cannot take any action.
2.4. I can solve all these problems if I change the permissions of the shared folder using chmod -R 755 /path/folder.
2.5- I have also discovered that the same thing happens on Windows clients, not only on Linux/Debian clients.
I know that at first I blamed the problem on file names, since the first issues I encountered involved names containing Ă‘ or accents. However, over time I noticed that the problems increased and were unrelated to file names. Finally, it seems that the issue is caused by the permissions of the local folder when it is created by the application if that folder is a shared folder with read-only permissions, as I explained above. On the web interface, I do not have any problems with these folders; it only happens during synchronization.
I hope I have explained myself more clearly. If you need more information, please do not hesitate to ask, and I will try to provide everything I can. If I need to post this in a specific forum or GitHub related to the application, please let me know.
Thank you very much for your patience.
P.S. Maybe I should change the title of the topic, since I have discovered that it is not related to special characters?