The problem is that Watchful, historically, fetched update information and updates once per extension across all of their clients and all their client sites. This meant that users were able to update their commercial extensions after their subscriptions expired as long as the download id for the single URL Watchful had checked was valid. We were forced to implement site specific update URLs to protect our business interests.
They had supposedly eliminated this issue but it appears that they may be doing something similar again or its possible that your domains have changed(?) . The update URL you have tells you what the problem is
Invalid access code - please login at JEvents.net to obtain an access code for your subscription . The current access code is for the domain wijkradenschalkwijk.nl compared to wijkraadeuropawijk.nl
Are one or both of these domains yours?
Its possible that you developed the site as wijkradenschalkwijk.nl but that is has been transferred to wijkraadeuropawijk.nl - if this is the case you should go to
https://www.jevents.net/updater-access-code and delete the old domain and create a new code for the new domain and update the setting on the client website