Latest update 20 March finally fixes the problem!
Mine doesn't even grey out. The Sim goes and talks to the other Sim, they go towards the cells, the other Sim goes inside the cell and is either cleaning or looking guilty. My police Sim sits at the computer, types a bit, then gets up, walks over to the cell door and the blue footprints appear overhead. Every single time.
At first I thought it was because my Sim was on Level 6 and the Cells were only available on Level 7, judging from the comments here it's an ongoing problem, but it doesn't appear in the list of issues on the Firemonkeys Support website.
I hope that, as EA are aware of the problem, there will be a way to reimburse everyone who has spent LPs to complete tasks that never happened.
