I have similar error the first time that i open a DB:
Network error
Reason: Network unavailable due to certificate issue. Try changing the
setting Use Windows trust store in Preferences->Connections and
restart DBeaver. It might help if you haven't overridden trust store.
javax.net.ssl.SSLHandshakeException:PKIX path building failed:
sun.security.provider.certpath.SunCertPathBuilderException: unable to
find valid certification path to requested target
I try 'bAsK' solution but not work for me.
The solution for me is remove check in the setting Use Windows trust store in Preferences->Connections and restart DBeaver

I also installed JRE 8 (Java)