I found I didn’t have a wp-content/uploads folder so I created one and set up permissions and ownership. Looks like I’m good now.
If you’re a Linux noob what I did was navigate to the wp-content directory and created the /uploads directory with:
sudo mkdir uploads
sudo chown root:www-data uploads
sudo chmod 755 uploads
So that’s a make-directory, a change ownership and change of access mode, i.e. read, write, execute, etc.
The “sudo” stuff is because I’m running Ubuntu which discourages the use of supervisor mode.