I double checked the code and think there must be something fishy in the state of your OH core framework, because …
… this line indicates the API login was scheduled (asynchronously, but immediately). I’d expect the execution of that login to produce another line like
XX:XX:XX.XXX [TRACE] [cs.internal.handler.EcovacsApiHandler] - API Login: Running one-shot
If that does not happen, it seems like the thing handler thread pool (which is supposed to provide a thread which then executes the API login task) is blocked. I’m not sure how/why, though. A thread dump might help - see e.g. here how to create one.