I fixed my own issue. Apparently some install scripts fail when run as root (or with sudo). I'm not sure why this is the case, but I got everything to work by running sudo chown -R ralph:www-data /path/to/nodebb && ./nodebb upgrade as a standard user.
Unable to Install Plugins
here is the error message I receive when trying to install plugins from the /admin site. The forum is running on an EC2 in AWS.
Did you forget the error message? Check permissions in the filesystem
Looks like you do not have write access to the volume your NodeBB is installed in.