Sim appears frozen

@Janie641, I have always used the resetsim <First name> <Last name> cheat.  So, for example you had Bella Goth that was stuck, you would type in the cheat box resetsim Bella Goth and then hit the Enter button. However, some are saying that this is no longer working correctly for them.

Therefore, you can try what @diopter77 suggested, but you will probably have to bring up the cheat box again and type testingcheats on to be able to shift  click on anything. 😉  For more on this see Carl's Sims 4 Guide and scroll down to the Testing Cheats section. 🙂 https://www.carls-sims-4-guide.com/cheats.php

Please update us on your progress! 😇

Not exactly the same thing but I have a cat who gets stuck on a table or in one specific room very often. I always just shift - left click on her (with testingcheats on) and reset. This has helped every time so far, although she sometimes goes right back to the same spot and gets stuck again. I've never had to do this more than 2 times in a row though.
I hope this works the same way for your sim.

@anneke33 Do you by any chance use the bb.moveobjects cheat when building? Because what you describe sounds like you have objects that were placed with that cheat enabled, such as clutter, which may then cause these routing/reset issues. Whenever a specific location repeatedly gets a sim (or sim pet) stuck like that, it usually indicates an object's blocking footprint. These footprints are invisible. You may also have too many objects on a surface without enough slots for them, or slots that are too small for the objects on them (yes, sometimes patches can change footprint sizes). Try moving around the objects in that room or on that table without that cheat enabled. You may even have to delete some of them, especially if they're from debug or have been changed in size with the bracket keys. This could solve your issue.

I hope this helped.

@DMDragonCT haha yes, I always use bb.moveobjects when I'm building - I love building more than actually playing -  and what you're saying makes sense, for the cat getting stuck on the table, at least, as that side table was put in place using moveobjects.
I have no idea why she gets stuck in that one room though, I only used moveobjects on the complete opposite side of the (quite large) room to place (another) side table right next to the sofa. The cat gets stuck on the other end, near the door. It's also just one cat that gets stuck and I have a total of 4 cats and 2 dogs + 2 sims in that house. The other pets and sims have no issue. It's always the same cat so I just pretend that she's a bit dumb and help her out when needed 😉 It doesn't really bother me very much atm but when it does, I'll keep your suggestions in mind! Thanks! 🙂

@anneke33 I really like the way you think! Too often players just get overly irritated at game quirks like that, so it's refreshing to hear that you "imagine" that this cat just has a slight problem. I also find it most intriguing that only this one cat of yours suffers that issue.

I always have moveobjects enabled as well, even while playing in live-mode, which is NOT something I recommend doing for beginners or casual players as it's easy to lose a plate or empty glass inside a wall or piece of furniture with a single misplaced click. The Sims 4 tends to receive a lot of unnecessary hate, but in my opinion, it is the most flexible and adaptive game-engine ever created when it comes to building and then interacting with that custom build.

By the way, welcome, and Happy Simming!

@DMDragonCT nah, minor things like that (or the bath/shower combo being buggy atm) don't bother me as they don't really affect gameplay and have easy fixes 😉 
If anything, the cat issue is funny to me because we used to have 4 cats (and 2 dogs) in real life and one of our cats was a bit on the dumber side too. Funnily enough, in my game I have a mom cat, dad cat and then their offspring, a male and a female. It's the young female who always gets stuck in the game. In real life, we had the exact same situation and it was also the female "kitten" that was a bit intellectually challenged 😃 It's like the game knows and it's bringing back a lot of fond memories 🙂 

Haha, I know! I also almost always play with moveobjects enabled. I've been playing and building since sims 1 came out so I usually don't lose things inside walls or objects, most of the time anyway 😃
I've noticed this too and it saddens me. Of course, as a builder, there are some things that I would like to see added - I really miss the option we had in sims 3 to change the color and texture of furniture piece by piece, and other things, of course - but I still think it's an excellent game for letting the creative juices flow. I'm not going to whine about things like that though and am happy with all the new things we get when a new expansion or stuff pack comes out 🙂 

Thank you and Happy Simming to you too! 🙂 

@DMDragonCT I forgot to mention that that same cat also has issues at the vet. Only that cat, again. Every other pet I have goes to the vet without problems but that one usually doesn't want to get on the table, or doesn't know how. I've had to try several times to get her examined every time I took het to the vet.  It adds to the experience of having a cat with an issue and it's funny to me 😃