I asked around, and it turns out rarepairfest had the same problem, which took a week and a half to fix (a week for AO3 to get back to them, another few days to actually fix it). They ended up sending out assignments by hand, which is a VERY tempting option and something we are looking into doing now that it looks like this will take longer than a day or two to resolve.
If anyone would like to know who they are going to be assigned to in advance of assignments going out, either email us at xmenremix13mods@gmail.com, or send us a signed-in ask at
the tumblr, and we would be glad to tell you! We have all the matches sorted out on a spreadsheet and they will NOT be changing at this point.
We will probably also be pushing the schedule back by a week. So remixes will most likely be due on September 11 now, with the collection opening on the 18th and reveals on the 25th.
ETA: Okay, AO3 got back to me already! I have added the AO3 support account to the collection so that they can take a closer look at it.
If it’s not fixed by the end of the weekend, and we don’t have an estimate for when it will be fixed by then, we will hand-email assignments out.