I am also seeing the same issue, but for only infospaces based on UNX universes. But it works for Hana based infospaces.
Unx based infopsaces works in our lower environment. I tried to create new indexing server, it is same issue.
SAP support suggested to add conection server dir path in to environment variables. But in lower environment it works fine without enviromenet variable.
-Djava.awt.headless=true -Dosgi.configuration.area=configuration.xxx_SIA.ExplorerExplorationServer -server -XX:MaxPermSize=256m -Dosgi.clean=true -Xmx8g -jar plugins/org.eclipse.equinox.launcher_1.0.101.R34x_v20081125.jar -loggingPath "C:/Program Files (x86)/SAP BusinessObjects/SAP BusinessObjects Enterprise XI 4.0/logging/" -connectivity_dir %CONNECTIONSERVER_DIR% -serverkind explorerIndexing