Good evening Frederique and welcome back!
Thank you for reaching out to us.
We are sorry to hear about that the plugin no longer works to your expectations after changing your website address.
I would love to help you with this topic.
The first thing I would recommend is re-saving your permalinks (this might help).
Secondly, could you provide me with an example (screenshot) of what you mean when you say the plugin is not working ? Are you getting an error message ? An unexpected page ?
The reason I am asking is because I just went to http://haaksbergenactueel.nl/agenda/ and could not see anything obviously wrong there.
Have a good week-end,
Geoff B.