Failed to create post

I am getting an error message, simply “failed to create post”:
failed_to_create_post
Also, I have done a search for Mastodon users and added, but they still do not show on my list.
I would assume this is a database thing, but I… have no actual idea.
My NC installation is hosted on a shared hosting, so I do not have a lot of log access. Any suggestions for troubleshooting the question?