Installing LOTRO wasn’t much of an issue but logging into play was, I kept getting

“An internal error has occurred please contact customer services.”

After much swearing I found a solid solution that fixed it, which I thought I’d post to help others with this same scenario.

If you receive this message, try to select another Language from the down-arrow icon in the top right of the Launcher. This will cause the client to relaunch and should then allow the Term & Conditions boxes to appear correctly and for the launcher to progress properly. You can turn the language back after the launcher has updated.