Bonus game material problems

[Nona]

I have already finished the game one and now I am going through the additional material. However, for some reason, the Maid Missions 12+ are consistently marked as not available to me, even though I have completed all the previous ones. I also cannot read the signposts at all, despite having finished all other available bonus material both in Asdivine and Reveria. The advice I have found on other forums about talking to a certain maid did not resolve this problem. Is this a bug, or am I missing something?