It’s been awhile since I made a campaign to share content in, so I’m not sure if I’m doing it wrong or if there’s a bug. I made a new campaign and sent my wife the link so that she could make a character. I have all the content on the site, and I’m a top tier subscriber. I enabled content sharing, but she could only see the base races when she made a character following the link. Eventually, I made a random PC and put them in the campaign, and then suddenly she had access to everything. I thought that as long as I was the owner of the campaign, the content was shared. Do I need to make a PC in the campaign too, now? Or am I misremembering?

When you send a player the campaign link they should have the option of either selecting an existing character to add or creating a new character, either of which should then open up the shared content in the character builder. If LurkyTheHatMan's entitlements sync (under Account > Marketplace) doesn't work (or if it shows that your entitlements data is already in sync), you might try having her sign out and back in, and if that fails, try contacting support. 

The character must be created within the campaign, either using the Create a Character button when you follow the join link or by using the Create Unassigned Character button on the campaign page.