Admin panel not available after fresh installation

Problem: 404 error with

I have ghost running on digitalocean (without docker). I followed the installation guide (1-click installation) and after some false starts, the admin panel was accessible yesterday. When trying to finish set-up today (e.g., upload a favicon), I got the error “resource not available” and the admin panel is not accessible.

Ghost: 4.21.0
Broswer: Firefox

ghost ls shows that the site is running.

output of ghost doctor

 Checking system Node.js version - found v14.18.1
✔ Checking logged in user
✔ Ensuring user is not logged in as ghost user
✔ Checking if logged in user is directory owner
✔ Checking current folder permissions
✔ Checking system compatibility
✔ Checking for a MySQL installation
+ sudo systemctl is-active ghost_blog-netnigma-io
Instance is currently running
ℹ Validating config [skipped]
✔ Checking folder permissions
✔ Checking file permissions
✔ Checking content folder ownership
✔ Checking memory availability
✔ Checking binary dependencies
✔ Checking free space
✔ Checking systemd unit file
✔ Checking systemd node version - found v14.18.1