I figured it out. I missed a side quest for the threesome with the MCs mom and sister. After that the missions started coming again.
Hopefully you figured this out ages ago, but I got back on track by setting up the Momoko/Airi threesome, once by asking both to sleepover on same night, once by peeking on Momoko in her room (afternoon?), and staying when spotted.
That unlocked some Sada content (wash her towel), still waiting to see how far that gets me.