Hi Gabrielle,
I’m sorry that you’re running into this issue, but I’ll be happy to help you out.
As a first step, can you try flushing your permalinks by going to Settings > Permalinks and clicking “Save”? Be sure to clear out any caching that you might be doing on your site, on your server or via a plugin.
If this doesn’t help, it could be that the latest versions aren’t getting along well with something else on your site. You can check for this by running through the steps outlined here – a plugin like Health Check can help speed up this process.
Please let me know what you find!
Thanks,
Jennifer