Can't invent items from Ambition's Ultimate Career Bundle

The first thing to do is to check out your content in a new save. You can use NRaas MasterController plus MC Cheats to grant inventing skill (click on a sim, NRaas > MC > Advanced > Skill Level), and DebugEnabler to teach a sim the inventions. If everything works, then it's just your current save, or maybe your current household or sim, that's somehow borked.

Otherwise, the pet shop not working makes me think your ccmerged.package might be corrupt. It's necessary to make premium store items function correctly. I'm not sure whether the Ultimate Career Bundle functions as premium content, but the pet shop cash register does. You can rebuild your own ccmerged by downloading all of your premium content and these two items into a clean game folder, then just replacing your old ccmerged with the newly generated one. Or you can skip all that work and download this file from NonaSims:

https://nonasims.wordpress.com/2012/05/17/dcbackup-ccmerged-package-and-your-premium-content-items/

Be sure to test the content in a clean game folder, just to make sure it's working. And, of course, delete your cache files before proceeding.

If rebuilding or replacing your ccmerged doesn't help, you likely have a corrupt .ebc file in DCCache. If you were reinstalling the content into that file, it would probably continue to not work properly. You could uninstall the Ultimate Career Bundle and pet store from your game folder and then reinstall them into a clean game folder. Then take your new .ebc file and rename it so that it's numbered one higher than the highest in your existing game folder (so if those are dcdb0.ebc through dcdb4.ebc, rename your new one dcdb5.ebc). Place this file in DCCache in your old game folder, grab the Library file that corresponds to the pet shop itself, put your old folder back in Documents\EA, and test things out.

In between trying Nona's ccmerged file, if that doesn't seem to help yet, and working directly with the ebc files, there is another step worth trying. Leave Nona's ccmerged where it is at that point in DCBackup but put a second copy of it in Mods\Overrides. Sometimes this helps when the problem is not with ccmerged itself but a timing issue with the order in which things load at startup.

I'm probably not the one to help you with a technical problem but you did say “any thoughts or ideas” so I'll say it sounds like a problem I had with a store item I bought, the MultiTab 6000. My sim would put his headset on and touch the tablet screen as if he was starting a tab-cast but then nothing would happen. The cause turned out to be an incorrect “fix” I did for a separate issue. I found a bad guide that told me to delete the contents of the DCBackup folder but neglected to mention that Ccmerged.package should not be deleted. Tricks to restore the file failed to generate the correct file, I eventually had to download a fixed Ccmerged file. Maybe this file has gone missing or is corrupt. The file should be in Documents\Electronic Arts\The Sims 3\DCBackup

Thanks for the reply @Satanu_Reeves. That is a good thought but I do have the ccmerged.package file in the dcbackup folder. I actually went back through some backups and found the file that was created when I installed all my store content on my current laptop and replaced the ccmerged file just in case the one in the folder had been corrupted somehow. It didn't help.

Another strange thing I noticed recently involves the pet store that came with the Pets Limited Edition expansion pack. I've never had a problem with it at all but last time I placed it in a game and sent a sim to buy something the special pet items were not available to buy through the pet store cash register. They were, however, still showing up inside the pet store (on display). So they are in the game just not available to purchase with the cash register. Something weird is definitely going on. I wonder if I somehow deleted some other important file somewhere while cleaning up my documents folder.

I'll have to compare my old backups with my current folder and see if something is missing.

Thanks @puzzlezaddict and @igazor. I'll give your suggestions a try.