Add ons are player created and supported. Add ons are designed to work the version of the Lotro software that they were created or last updated for. As Turbine changes the game, the add ons will stop working properly. You need to contact the author of the malfunctioning plug in. Hopefully, they will update the plug in to work with the current version of the game software.
Originally Posted by Goldfur
The big difficulty is that the authors make and maintain the plugins as a labor of love when they have time and feel like it. Eventually, most authors decide to stop supporting their plug in. In which case, you have to update it yourself. Or try and find someone that is willing to update it for you.
Unless stated otherwise, all content in this post is My Personal Opinion.