You know, the more I think about it, the more I'm beginning to think it is something glitched with the sim. I've got a similar thing going on with a sim who used to be able do something but now can't no matter what I do. So I think that sim is permanently glitched somehow. But I'm pretty sure when whatever it was happened and how it happened so it might be related.
So @aodoherty was the sim that can no longer do the serenade option playing that instrument using that option when you had another sim in the household travel, leaving the sim playing the instrument behind?
Here's why I ask. Household of 8 sims. I had a sim writing a research paper (DU added option after leveling up on Research and Debate Skill) on a laptop. I also had 6 other sims doing skill things at the time too. I had the remaining member of the household travel to Glimmerbrook alone leaving all the others doing whatever they were doing when that travel happened. While I was off with the solo sim, I clicked the portraits to have them continue building skills or socialize. When I got back though and went to send the sims I left behind back to what they were doing when I left, the one who was writing the Research paper no longer had the option on her computer and there was no resume option anywhere that I could find. I tried changing out computers, etc. But the option has not reappeared for just that one sim on any computer. Every other sim in that household and other households can still do it. Just not her. So I think I've got a glitched sim maybe and I'm hoping maybe something in a patch will fix the problem at some point. It's a very minor issue and really doesn't affect play but for that single sim.
But I wonder after all you tried that maybe you've got something similar going on with your sim and that's why I ask the question. So was travel involved?