Even if you have a large desk for the computer, I find that if you put items on it, it will cause these issues. Especially if you're using a large screen computer. For example, the yellow gaming computer that you can get as a reward from the video game streaming career. You can have the biggest desk for that computer, but if you put the quill pen, or a lamp that is not a computer lamp, or a flower, or almost anything, if you put it on the desk it will not function properly often. Even if it did the day before, the next day it might not. This is just something I have noticed in my game. Maybe not the same as in yours. But if you have items on the desk, try removing them. Also, if you placed the desk using "moveobjects on" that can cause problems too. Not as often as items on the desk but it can.
One other thing that causes problems like that is lights that hang from the ceiling. If you have short walls, many of those lights the sims can't walk under. And they don't give a routing error thought bubble either. It took me a while to figure this out because my butler and sims would not clear dishes from a table. And it turned out to be the light hanging above the table. So even though they didn't have to walk under it, they still couldn't clean up the dishes off of the table. So check your hanging lights and move or replace them with shorter ones because that is a HUGE problem in short and medium walled houses. I hope something here helps some of you.
