My Lifespan settings are fine. yeah i have MCCC but never had a problem before the update. MCCC yeah can customise lifespan but it messes about with the Un plaayed sims. I have already tried this gave young adults 80days and all the unplayed sims ended up with 204.
I know people hate when we ask this...
Can you take out your mods (either disable, or move the folder to desktop, or both), open to see if it looks correct, and then exit without saving? You don't have to save without mods and CC, that would lead to naked Sims if you have CC, just... to confirm that it's really the game and not the mods.
Other people are having similar issues with MCCC. I'm also an MCCC user, so I checked their Discord and this is a known issue that will be fixed in the next release. They recommend manually setting your desired lifespan settings as "normal" in the mod itself. I believe this is under MCCC > MCCC Settings > Set Age Span Duration > Human, but if you have any problems or questions it would probably be better to ask MCCC support. They're really busy after the latest patch, though, so please be patient and kind with them.
If you join their Discord this info is pinned in the help channel.
Confirming this is mod related and MC Command center. It's not even necessary to remove the mods. Just uncheck the enable mods and custom content. Restart your save with long or short lifespan on. Then it will be updated automatically. You can either play without MC Command center or just use normal life span until they update it.
There is a problem with long and short life spans if you have MC Command Center installed. If you choose to play with it, you need to leave the game setting on normal lifespan. Then change the lifespan days for each category to what you want like 80 days for young adults. If you have the setting on Long and then change the days, it won't work right. They are aware of the issue, but are fixing it in a general release since there is a work around. I'm not sure when it will be fixed.
