@BadGalMsJo each issue needs reporting separately but did you select the kelp from your inventory and ask them to eat it the same as with fruit or veg and did you then send them into the water to transform? You need to do that within a time limit to turn them into a mermaid in the sea. They should get new moodlets when they eat the kelp too. Then send them for a swim.
If they don't transform in the sea do they have the gardening dislike in their Likes/Dislikes in CAS (because that would match a recent bug report) and are they already an occult Sim? So a Vampire/Werewolf/Spellcaster?
For the other issues did you start a New Game from the Main Menu and create a test Sim for the other issues to see if a new game is affected with the mailbox/phone/PC because if a new game isn't affected you could save your Sim to your library and retrieve them to place them in a fresh game.
The current save game seems compromised somehow, have you seen any error codes or downloaded a lot from the Gallery and seen any issues? It wouldn't be just one bug causing several issues. It would be multiple bugs but some are more likely technical issues.
Edit: found a bug report you've just filed but it will possibly be closed and you'll probably be asked to file separate ones for each problem as we keep each issue separate. On each bug report too, could you add what we've already tried so you're not asked to do them all again as someone else will probably ask you to go over the troubleshooting steps we've already gone over.
So if you just add a note to each report saying you've power cycled the console, checked everything is up to date, uninstalled and reinstalled content, cleared locally saved data, found that NPCs are not affected, marked as unplayed, moved them to Other Households, cleared any cheat codes, tested a new game if you've done that last one. You can just cut and paste this onto each report if it will save time. Otherwise you'll probably be asked to do some of the things you've already done. I think that's everything we've tried.
Also your game version number should be 1.89.2.2310. It's incorrect on the bug report but it's really important that it's correct as if it isn't that would explain some of these issues. If you go to Manage Game and Add-ons by using the circle with 3 lines on it you will see it on the Sims 4 info panel on the right hand side of the screen. I'll add images again to show you where to find it.
Ok and I have it in the inventory and it just says out into world nothing about eating it. It didn’t say anything about enter the water also the sim is a non occulant sim that was already made. Yes the sims 4 has the newest update the version 1.89.2.2310. I’ll try the new game update next just wanna figure out why nothing is working.
