[Bug]: [PopOS/Cosmic; AppImage] App launches, but is totally unresponsive

[jarekdudzinski]

PopOS 24.04 Cosmic DE

After launching, the window shows up but is unresponsive: I cannot close it nor click any button.
When started from terminal, it throws those errors:

Nextcloud-4.0.0-x86_64.AppImage
qt.qpa.plugin: Could not find the Qt platform plugin "wayland" in ""
Failed to initialize instances shared memory: "QSharedMemory::handle: doesn't exist"

Tested both latest app (from website) and the latest version 4 build.
Top bar menu - the same, not responsive. It shows up when I click icon, but nothing happens when I click any option.

The only way to close it is to kill process.

Steps to reproduce

1. Download
2. Run

Expected behavior

I should be able to use it?

Which files are affected by this bug

Nextcloud-4.0.0-x86_64.AppImage, Nextcloud-3.17.3-x86_64.AppImage

Operating system

Linux

Which version of the operating system you are running.

PopOS 24.04 Cosmic

Package

Official Linux AppImage

Nextcloud Server version

latest

Nextcloud Desktop Client version

3.17.3, 4.0.0

Is this bug present after an update or on a fresh install?

Fresh desktop client install

Are you using the Nextcloud Server Encryption module?

Encryption is Enabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

Additional info

No response

[theroch]

Same problem on Windows 10 x64 with Nextcloud 4.0.1.

[theroch]

I've downgraded back to nextcloud client 3.17.3. But the problem still exists.

I've monitored the nextcloud app with the process monitor and found out, that the client wants to read the file .sync-exclude.lst in the root of my local cloud storage. The read resulted in 0xC000CF18. After that, the operation QueryAllInformationFile resulted in Buffer Overflow. The nexcloud client hangs in an endless loop, which results in an unresponsive nextcloud app and unresponsive Windows explorer. The file .sync-exclude.lst is marked as available if online in the Windows explorer.
I've killed the process nextcloud.exe. After that, I've checked if the file .sync-exclude.lst exists remotely on the server. The file doesn't exist remotely. I tried to open the file with an editor, which results in an error. So I've removed the problematic file .sync-exclude.lst locally, by deleting it via explorer.
After that, the nextcloud client starts normally and all works normal again.
So I've found and solved the problem in my case.
Maybe this is helpful for your problem on Linux?

Update 1:
I've upgraded from 3.17.3 to 4.0.1 and the client is working properly.

[theroch]

@jarekdudzinski
You can try to install the QT6 wayland plugin:
sudo apt install qt6-wayland

[nilsding]

@jarekdudzinski thanks for the report, I'd like to get some more information:

• What GPU (and driver) do you use?
• Does right-clicking on the icon to open the Settings window work?
• Is there any other Nextcloud process running? (ps -ef | grep -i nextcl)

---

@theroch that will not work with the AppImage, as it does not depend on a system-provided Qt -- instead the AppImage has a (usually much newer) Qt version embedded.
for the Windows-specific issue you may want to add your finding to #8915.

[theroch]

@nilsding

#8915 does not have the same symptoms.
I've created #8984 to describe the issue and solution.