Please check connection, Mattermost unreachable. If issue persists, ask administrator to check WebSocket port

I have mattermost running on a qnap NAS (not in a container!) and mattermost-desktop 5.2.2 on a linux box.
Problem: Please check connection, Mattermost unreachable. If issue persists, ask administrator to [check WebSocket port
Seems like it has to do with the certificate on the server (Let’s encrypt in my case). Mattermost via browser works ok, but mattermost-desktop won’t allow editing and leaves the text field yellow.
Any ideas?

Hi @masaka and welcome to the Mattermost forums!

Are you sure you have Mattermost server I’m not aware that such a version exists and if so, it’s very, very old.
Can you please check the exact version in your “About” screen again when connected via the browser?

You can also connect to this URL and scroll down to the bottom to see the Version attribute:


Thanks for your reply.
Yes, it is indeed version I know it is old, very old even, but qnap hasn’t updated it.
If I do what you are suggesting I get version 5.0.0.
Meanwhile I uninstalled mattermost from my server and reinstalled it. Did the same with mattermost-desktop. Now it is working again as it should but I do not really understand why.

Interesting - so after reinstalling, Mattermost desktop also works with the Mattermost server installed on your QNAP?

I had to reinstall both, Mattermost on the qnap nas and mattermost-desktop on all the linux boxes that connect to the nas. For some unknown reason mattermost started working again as before.
BTW I did not change the configuration.

Alright, thanks for the answer.
Since you’re running Mattermost on QNAP: Could you have a look at the following thread and maybe helpe me help the other user here to find out where the directories are?

OK, here is the whole story.
As you mentioned yourself, qnap’s default app is old but qnap club offers a more recent version (
That I installed but couldn’t open. Next I looked into the file system with putty and ssh. There I found that the default version is located under /share/CACHEDEV1_DATA/.qpkg/mattermost whereas the new version is found under /Mattermost. In other words, the new version does NOT overwrite the old one!
So far so good. Since I failed to open the new version, I then completely deleted both folders. After several new starts of the nas (TVS-463) I reinstalled the default version. And to my surprise everything worked as before.

Hi masaka,
just a question : Mattermost and you got all the previous database of MM ?
or you have at least installed and kept the old original 5.0 ?
Just an idea: new one could be installed using a container…

Yes completely wiped. BTW, I installed MM desktop on a new box today and experienced the same problem again. It seems that all depends on the version. When I changed to a different version, all was fine. But I am still using the old on the server provided by Qnap.