Cannot run programs in my prison

You need to assign more "Work" hours in the regime tab.

If you have a closer look, by default there are only two consecutive work-blocks. Some programs need three (or more?) consecutive work blocks. So does the educational lesson.

The feedback "ALL ROOMS BOOKED" is not very helpful here, I ran into that, too.

Thank you for confirming it was "work" @Amadeus9.