Also upgraded from 3.2 to 3.3 but no webinterface.
Only on port is active:
penhabian@OpenHAB1:~ $ sudo netstat -tulpn | grep java
[sudo] password for openhabian:
tcp6 0 0 127.0.0.1:43805 :::* LISTEN 869/java
Is behavior persistent across restarts ?
See if bundle:list in console shows any non-“Active” bundle and eventually start it (bundle:start).
Eventually clear the Karaf cache (search forum there’s a post explaining it).