I tested in my home computer, and clicking ComfortUpdate opens some TCP connections and it seems to work. On a server I got "It seems that the ComfortUpdate server is not responding. Please try again in few minutes or contact the LimeSurvey team." and if I try to put in the key, I got

PO-Revision-Date: 2020-02-26 16:08:12+0000 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Plural-Forms: nplurals=2; plural=n != 1; X-Generator: GlotPress/2.3.1 Language: en_US Project-Id-Version: LimeSurvey 4.x.x PO-Revision-Date: 2020-02-26 16:08:12+0000 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Plural-Forms: nplurals=2; plural=n != 1; X-Generator: GlotPress/2.3.1 Language: en_US Project-Id-Version: LimeSurvey 4.x.x

Where to start debugging, or to what server should the system connect and what ports should be open etc?

I am using Version 4.1.11+200316, RHEL 8, MariaDB.

Found. It was SELinux forbidding the connection. But maybe it's worth noting in some manual that in RHEL 8 (at least) you must say

setsebool -P httpd_can_network_connect on

to get ComfortUpdate to work.

And now for the next problem: "Unknown update key ! Your key is unknown by the update server."

Is there some site where I could check that my key is valid?

Jmantysalo wrote: Found. It was SELinux forbidding the connection. But maybe it's worth noting in some manual that in RHEL 8 (at least) you must say

LimeSurvey manual cannot cover OS topics. Where to stop? That ComfortUpdate needs a connection to a different server shouldn't surprise anyone.

Jmantysalo wrote: Is there some site where I could check that my key is valid?

No. Where did you get your key from? You can find your key in the user profile when you logged in on LimeSurvey.org.

If you still have issues, you can open a ticket via support here on limesurvey.org

jelo wrote: Where did you get your key from? You can find your key in the user profile when you logged in on LimeSurvey.org.

If you still have issues, you can open a ticket via support here on limesurvey.org

We have other group at university that handles licenses, I just install software etc. Hence the key is not linked to my profile.

I'll make a ticket.

jelo wrote: LimeSurvey manual cannot cover OS topics. Where to stop?

:+1: !! agree at 100%