Hi,
A couple of points.
The certificates will install without error in most cases. However, if you do not install the certificates while logged on to the NPrinting server with the service account used to run the NPrinting server, the certificates will not work as expected.
Second, the initial error is a port 4242 error. You need to ensure that the ports are open between the NPrinting server and the Qlik Sense server. This means the necessary ports need to be open as specified in the help page below not only on the NPrinting and destination server computer windows firewalls but also on any network hardware/software/cloud based firewalls that may also be blocking the required ports.
https://help.qlik.com/en-US/nprinting/April2019/Content/NPrinting/DeployingQVNprinting/Ports.htmPlease also check all the points in the following support article which include the points above as well.
https://support.qlik.com/articles/000028729Hopefully this information guides you in the right direction. If this doesn't help, I suggest started a support ticket with us.
Kind regards...
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