Sims 4 is not a game you can play well, without being willing to do some reading.
Using mods and custom content (CC) is no different, and it may even be MORE important, to read the details about what you're thinking of adding to your game.
Why? Basically, because patches from EA change code, and every file in your /Mods folder is, at its basic level, "all code." (YES, things like cc hair and clothes and tables and plants can, and do, break. Everything "extra" can.) Things made to work with prior game versions can stop working at any time, unless they're updated, depending on what areas of code EA just "touched."
Luckily, Sims4Studio (package editor program) can address many errors EA has "added to" older custom content files, through their CAS and Object batch fixes. If you're going to have cc clothes/etc and cc objects, you Really Need to install, and keep updated, Sims4Studio.
Gratuitous plug for MC Command Center, if you settle in and take some time to read through the options it can offer you, you may find yourself able to remove a lot of other, smaller (and possibly now-broken or abandoned) mods.
At the very least, it would be well worth your time to open up the Overview page on Deaderpool's website and browse. ALL of the settings for MCCC are appended to the bottom of that page, and CTRL-F works fine, if you know what you're looking for.
Pretty much any Script Mod dated before November 2017 (Cats and Dogs) is NOT still going to be working properly. And the (later) 1.40 patch introduced an "appearance modifier" error that again required updates for SEVERAL game-changer mods (both script and regular package types), just to give you some tips on known previous breakage.
Keeping your mods and cc up to date is necessary if you want to spend more time PLAYING than you do tracking down and fixing error messages.
Read any info available wherever you download them from. In the case of CC, you may need to download a separate "mesh" file, also.
MTS (Mod the Sims) is well organized, with a Description page, a tab for downloading Files, and a tab for Comments.
Reading the Description page, and also making sure you have the CORRECT File version for the current game patch, is advised.
Checking Comments is usually a great way to judge whether a file is still working.
There's a comprehensive mods/cc Tip Sheet, here.
And if you find yourself needing to single out broken files, read this post.
Still need help figuring out what's wrong? Bring your newest lastException.txt (without numbers if possible) to us on Deaderpool's Discord.
Good Luck with the Seasons patch!!
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