Hi Harjo,
Please see my answers below,
"on which server do you have installed that certificate?
on the running server, that run’s the headless-client? → Yes, I have installed certificate on the running server where the headless client running.
" the headless client is trying to get an url from another server with ssl??, → Actually, I am doing auto solution update in the headless client for the same running server and tried to access the solution update method by accessing the https url of the running server, like, “https://xxx.com/servoy-admin/solutions/import”, which causes the problem and asking to import the certificate to the java/cacerts though the certificate is existed already in cacerts. Hope it’s clear.