Just throwing this out there because I'm in a mood.
Using live chat can be irritating. Only used a few times personally and never will again but here are a couple of tips.
If you are waiting and waiting for the tech to begin, try minimizing your page and all tabs. The chat screen may be hiding in a new window behind the one you're on.
If you're disabled like me or just a slow typist, write up a message to that effect with a plea for patience, copy, and have it ready to paste when your chat session starts. Hopefully this will prevent you from being cut off before you can type your first few words. You can also use partial sentences. Ideally you'll write up all your issues before hand, including your computer type and what fixes you've tried, to paste when asked.
Expect to be treated like an idiot. You know what your problem is but may be told that you are wrong and there is in fact no problem. (Oh so very friggin helpful and unfortunately true) You may need to be very clear and stick to your guns.
If your question involves a specific page have the link to that page ready. If you try switch tabs to go back and copy that link to paste, as you may be asked to, your session will end.
While personal chat experiences have been with people who have never heard of "customer service" they can't all be that bad. (Can they?) However, the people I've spoken to on the phone have been flat out AWESOME. They seem to actually care, have patience and a willingness to walk you through steps you may not understand.
Not looking for xp, just hope this helps someone.
Not sure how this applies to my original post and I'm for sure no techie but this is one possible solution that doesn't involve mods. Do you use "testing cheats" to keep your sims awake? Hey, there just ain't enough time in a sim day, right? If your sim doesn't sleep at all they will eventually begin to fade. They'll stop changing clothes though go though the motions. Picture will disappear in icon then sims will vanish even if still playable. By the time they vanish, next time you start up they'll be gone.
Solution? Let them sleep every day even if only a few minutes.
This is just one potential reason for invisible sims and the only solution I know that can be discussed here.
Hopefully one of the wise ones that help on this site can give you more info. You may want to start a new post to get their attention as my original post was just a rant and they may not look here again.