Hello! @Wim De
Welcome to the LastPass Community.
Unfortunately at this time we cannot offer you a tool that double check if the credentials are still valid or not, since these depend on the 3rd party to be exactly from the website or service where you are using those credentials. At this moment the only option to double check if those credentials or Urls are still valid will be trying one by one.
In case you get an error related to the website, most likely is because the website no longer exists or if we say problem with the credentials, maybe you will have to reset those credentials for that website.
Please let me know if you need additional help.
Greetings!
Verlaine | Customer Care
