We would advise that you re-run the "install-boot" script to install the startup script (as described here: https://doc.dataiku.com/dss/latest/installation/new_instance.html#optional-enable-startup-at-boot-time)
If it does not work, you can still start DSS manually with DATA_DIR/bin/dss start and have a look at the "install-boot" script to add it at startup manually.