[sualfred]

@Montellese 
Ah, that's why. For some reasons the auto discovery of my Emby server does not work here. Never found out the issue and I have to manually add the connection details in Emby for Kodi or EmbyCon. 

@LongMan 
They changed the login method in v4, yes. Emby for Kodi and EmbyCon are handling it differently.

Let me quote a reply of @null_pointer to the question "Just wondering why embycon needs to authenticate on each start and emby for kodi does not."

It is because of the access token that the Emby server uses to authenticate requests.

A client authenticates using the username and password and the server returns an access token that is then used in requests.
This access token can also be stored and used in later requests.
If the client stores the access token in some sort of persistent storage mechanism then it can use the access token next session without having to re-authenticate the user.
If the access token is not stored in persistent storage then the client will need to re authenticate each session.

E4K and EmbyCon use different approaches for this.
EmbyCon does not store the access token between client sessions and re authenticates each time a user starts Kodi or a user is changed with fast user switching.