For the 3rd day Melody is not adding any items at Myterious Melody. In addition to at least always the lowest on list (latest arrival?) user. Do they probably not get an event that they have been added to a group? - or just a coincidence? Melody also never climbs up to top on the participant list, like she always did.
I've had the same experience. Melody has decided she no longer has the Lumi spirit. yesterday only myself and one other person submitted gifts. not sure if the others meant to or they are bugged like melody has been for the last few days.

She just got tired and went back a little too early.
(That is to say, yea, the last couple of the year apparently she's just not going to join. Ah well, at least it was only a couple, i'm not going to hound Keith to fix it, enjoy your holidays.)
This has been fixed! Melody ran out of sP, and that's why she didn't purchase anything. There's more details here: https://kumos.subeta.net/changelog/25.