Also, please note that in Venus 2.80, the rootfs is now read-only. To install the service, you need to remount it rw (which you can do with the script /opt/victronenergy/swupdate-scripts/remount-rw.sh), and then the service needs to be installed in /opt/victronenergy/service instead (which is overlayed onto /service at bootup, but reset to original at each boot).
You didn’t say what Venus version you are using, but if you are strugling with 2.80, go back to 2.72 and get it working there first.