UFW blocks cron job server on port 3333, until reloaded

Question

I have a web server (suave.io) running on port 3333. UFW shows the port to be allowed.

On reboot, the server is unreachable (despite running successfully). Once UFW is reloaded, 3333 is accessible.

What could be causing this?

Any ideas or guesses on what might be causing this would be very helpful.

Answer 1

Stumbled on an answer in a related search. Why UFW has to be (re)started at boot time if it's only iptables rule manager?

sudo invoke-rc.d iptables-persistent save