After upgrading to Nexus Repository 3.26 or higher startup fails with the following error seen in the logs:
ERROR [jetty-main-1] *SYSTEM org.sonatype.nexus.bootstrap.jetty.JettyServer - Failed to start
java.lang.IllegalStateException: KeyStores with multiple certificates are not supported on the base class org.eclipse.jetty.util.ssl.SslContextFactory. (Use org.eclipse.jetty.util.ssl.SslContextFactory$Server or org.eclipse.jetty.util.ssl.SslContextFactory$Client instead)
The error indicates that the $installdir/etc//jetty/jetty-https.xml file was copied from the previous installation. The format of this file changed in the Nexus Repository 3.26.0 release.
As a general rule, you shouldn't copy files from the previous version's installation directories to the new version.
See here for how to fix this specific issue by editing the etc/jetty-https.xml file and making a simple change: