when opening the invite, the dance background seems to be gone but theres still the HAs & Boudewijn's response on the page. ive open a number of letters but still no duel? does it take really long or has it expired?

are you talking about the Hastily Written thingies? Those are from a previous site event and have nothing to do with NPC Boudewijng duelling with you.

You get challenges from NPC Boudewijn when you go to the ballroom after a dance invite/acceptance. It's random.

ah i see. ive been trying to get the Boudewijn achievements by opening the . do i keep opening it until i get it? or is it not related? i wasnt here for the 2015 masq so im unfamiliar w the process

not related to any item in any way.

Dance with someone, whether they invite you or not. Click the link that takes you to the ballroom. Once this page resolves, you may get a Random Event over and on top of that page in which you are challenged by him.

ah alright. thank you!

you are welcome