Django site is not opening up on Digital Ocean Ubuntu droplet

Question

We have been using this server for an year already as our Django application development server but it stopped launching the site on whatever port we start the application. Digital Ocean hosting support said the issue should be with the application. Iḿ wondering what we are missing?

$ ps -ef | grep runserver 
 rmbl      1424    1414  0 05:02 pts/0    00:00:00 grep --color=auto runserver 
 -----------
 $
 $ sudo nmap -p 4000, 22 > 136.189.5.1 -Pn 
 Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-02-29 05:03 UTC 
 Nmap scan report for 22 (0.0.0.22) 
 Host is up.
 
 PORT     STATE    SERVICE 
 4000/tcp filtered remoteanything

 Nmap scan report for rmbl-s-1vcpu-2gb-ams3-01 (136.189.5.1) 
 Host is up (0.000082s latency).

 PORT     STATE  SERVICE 4000/tcp closed remoteanything

 Nmap done: 2 IP addresses (2 hosts up) scanned in 2.15 seconds
 ------------
 $
 $ sudo ufw status Status: active

To                         Action      From
--                         ------      ---- 
OpenSSH                   ALLOW       Anywhere
8080                      ALLOW       Anywhere
8000                      ALLOW       Anywhere                   
5432                      ALLOW       Anywhere                   
4000                      ALLOW       Anywhere                   
OpenSSH (v6)              ALLOW       Anywhere (v6)              
8080 (v6)                 ALLOW       Anywhere (v6)              
8000 (v6)                 ALLOW       Anywhere (v6)              
5432 (v6)                 ALLOW       Anywhere (v6)              
4000 (v6)                 ALLOW       Anywhere (v6)             
----------------------
$ 
$ sudo netstat -lanp | grep 4000 
$ 
$ sudo nmap -p 4000, 22 136.189.5.1 -Pn 
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-02-29 05:07 UTC 
Nmap scan report for 22 (0.0.0.22) 
Host is up.

PORT     STATE    SERVICE 
4000/tcp filtered remoteanything

Nmap scan report for rmbl-s-1vcpu-2gb-ams3-01 (136.189.5.1) 
Host is up(0.000082s latency).

PORT     STATE  SERVICE 4000/tcp closed remoteanything

Nmap done: 2 IP addresses (2 hosts up) scanned in 2.14 seconds 
$  
$ ps -ef | grep runserver 
jenkins     1679       1  1 05:05 ?        00:00:00 /var/lib/jenkins/workspace/dev-rmbl-project/env/bin/python manage.py runserver 0.0.0.0:4000
jenkins     1691    1679  1 05:05 ?  00:00:01 /var/lib/jenkins/workspace/dev-rmbl-project/env/bin/python manage.py runserver 0.0.0.0:4000
rmbl      1727    1414  0 05:07 pts/0 00:00:00 grep --color=auto runserver 
$ 
$ sudo nmap -p 4000, 22 136.189.5.1 -Pn 
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-02-29 05:08 UTC 
Nmap scan report for 22 (0.0.0.22) 
Host is up.

PORT     STATE    SERVICE 
4000/tcp filtered remoteanything

Nmap scan report for rmbl-s-1vcpu-2gb-ams3-01 (136.189.5.1) 
Host is up (0.000078s latency).

PORT     STATE  SERVICE 
4000/tcp closed remoteanything

Nmap done: 2 IP addresses (2 hosts up) scanned in 2.13 seconds 
$ 
$
$wget http://136.189.5.1:4000
--2024-02-29 13:44:39--  http://136.189.5.1:4000/ 
Connecting to 136.189.5.1:4000... failed: Connection refused.