I found that I have not installed nginx server so I followed your suggested video and  \(30\)\ How\ To\ Enable\ Multi\ Processing\ In\ Odoo\ \|\ Configure\ Workers\ In\ Odoo\ \-\ YouTube\.\ But\ I\ still\ get\ the\ same\ problem\.

Here's\ my\ files\.\ I\ do\ not\ use\ SSL\ so\ I\ skipped\ the\ SSL\ setup\ in\ the\ nginx\ default\ config\ setup 

/etc/nginx/sites\-available/default

upstream\ odoo\ \{
\ \ \ \ \ \ \ \ server\ 127\.0\.0\.1:8069;
\}

upstream\ odoochat\ \{
\ \ \ \ \ \ \ \ server\ 127\.0\.0\.1:8072;
\}

server\ \{
\ \ \ \ \ \ \ \ listen\ 80\ default_server;
\ \ \ \ \ \ \ \ listen\ \[::\]:80\ default_server;

\ \ \ \ \ \ \ \ proxy_read_timeout\ 720s;
\ \ \ \ \ \ \ \ proxy_connect_timeout\ 720s;
\ \ \ \ \ \ \ \ proxy_send_timeout\ 720s;

\ \ \ \ \ \ \ \ \#\ Add\ Headers\ for\ odoo\ proxy\ mode
\ \ \ \ \ \ \ \ proxy_set_header\ X\-Forwarded\-Host\ \$host;
\ \ \ \ \ \ \ \ proxy_set_header\ X\-Forwarded\-For\ \$proxy_add_x_forwarded_for;
\ \ \ \ \ \ \ \ proxy_set_header\ X\-Forwarded\-Proto\ \$scheme;
\ \ \ \ \ \ \ \ proxy_set_header\ X\-Real\-IP\ \$remote_addr;

\ \ \ \ \ \ \ \ \#\ log
\ \ \ \ \ \ \ \ access_log\ /var/log/nginx/odoo\.access\.log;
\ \ \ \ \ \ \ \ error_log\ /var/log/nginx/odoo\.error\.log;

\ \ \ \ \ \ \ \ \#\ Redirect\ longpoll\ requests\ to\ odoo\ longpolling\ port
\ \ \ \ \ \ \ \ location\ /longpolling\ \{
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ proxy_pass\ http://odoochat;
\ \ \ \ \ \ \ \ \}

\ \ \ \ \ \ \ \ root\ /var/www/html;

\ \ \ \ \ \ \ \ \#\ Add\ index\.php\ to\ the\ list\ if\ you\ are\ using\ PHP
\ \ \ \ \ \ \ \ index\ index\.html\ index\.htm\ index\.nginx\-debian\.html;

\ \ \ \ \ \ \ \ server_name\ _;

\ \ \ \ \ \ \ \ location\ /\ \{
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \#\ First\ attempt\ to\ serve\ request\ as\ file,\ then
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \#\ as\ directory,\ then\ fall\ back\ to\ displaying\ a\ 404\.
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ try_files\ \$uri\ \$uri/\ =404;

\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \#\ Redirect\ requests\ to\ odoo\ backend\ server
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ proxy_redirect\ off;
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ proxy_pass\ http://odoo;
\ \ \ \ \ \ \ \ \}

\ \ \ \ \ \ \ \ location\ \~\*\ /web/static/\ \{
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ proxy_cache_valid\ 200\ 90m;
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ proxy_buffering\ on;
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ expires\ 864000;
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ proxy_pass\ http://odoo;
\ \ \ \ \ \ \ \ \}

\ \ \ \ \ \ \ \ \#\ gzip
\ \ \ \ \ \ \ \ gzip_types\ text/css\ text/less\ text/plain\ text/xml\ application/xml\ application/json\ application/javascript;
\ \ \ \ \ \ \ \ gzip\ on;

\ \ \ \ \ \ \ \ client_body_in_file_only\ clean;
\ \ \ \ \ \ \ \ client_body_buffer_size\ 32K;
\ \ \ \ \ \ \ \ client_max_body_size\ 500M;
\ \ \ \ \ \ \ \ sendfile\ on;
\ \ \ \ \ \ \ \ send_timeout\ 600s;
\ \ \ \ \ \ \ \ keepalive_timeout\ 300;
\}

Here's\ the\ latest\ log:
The\ above\ exception\ was\ the\ direct\ cause\ of\ the\ following\ exception:

Traceback\ \(most\ recent\ call\ last\):
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http\.py",\ line\ 639,\ in\ _handle_exception
\ \ \ \ return\ super\(JsonRequest,\ self\)\._handle_exception\(exception\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http\.py",\ line\ 315,\ in\ _handle_exception
\ \ \ \ raise\ exception\.with_traceback\(None\)\ from\ new_cause
Exception:\ bus\.Bus\ unavailable
2023\-06\-08\ 08:36:55,769\ 1399\ INFO\ hago\ werkzeug:\ 101\.78\.142\.90\ \-\ \-\ \[08/Jun/2023\ 08:36:55\]\ "ESC\[37mPOST\ /longpolling/poll\ HTTP/1\.1ESC\[0m"\ 200\ \-\ 1\ 0\.000\ 0\.003
2023\-06\-08\ 08:37:02,646\ 1398\ ERROR\ hago\ odoo\.http:\ Exception\ during\ JSON\ request\ handling\.
Traceback\ \(most\ recent\ call\ last\):
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/addons/base/models/ir_http\.py",\ line\ 237,\ in\ _dispatch
\ \ \ \ result\ =\ request\.dispatch\(\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http\.py",\ line\ 683,\ in\ dispatch
\ \ \ \ result\ =\ self\._call_function\(\*\*self\.params\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http\.py",\ line\ 359,\ in\ _call_function
\ \ \ \ return\ checked_call\(self\.db,\ \*args,\ \*\*kwargs\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/service/model\.py",\ line\ 94,\ in\ wrapper
\ \ \ \ return\ f\(dbname,\ \*args,\ \*\*kwargs\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http\.py",\ line\ 347,\ in\ checked_call
\ \ \ \ result\ =\ self\.endpoint\(\*a,\ \*\*kw\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http\.py",\ line\ 912,\ in\ __call__
\ \ \ \ return\ self\.method\(\*args,\ \*\*kw\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http\.py",\ line\ 531,\ in\ response_wrap
\ \ \ \ response\ =\ f\(\*args,\ \*\*kw\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/addons/bus/controllers/main\.py",\ line\ 35,\ in\ poll
\ \ \ \ raise\ Exception\("bus\.Bus\ unavailable"\)
Exception

The\ above\ exception\ was\ the\ direct\ cause\ of\ the\ following\ exception:

Traceback\ \(most\ recent\ call\ last\):
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http\.py",\ line\ 639,\ in\ _handle_exception
\ \ \ \ return\ super\(JsonRequest,\ self\)\._handle_exception\(exception\)
\ \ File\ "/usr/lib/python3/dist\-packages/odoo/http.py", line 315, in _handle_exception
raise exception.with_traceback(None) from new_cause
Exception: bus.Bus unavailable
2023-06-08 08:37:02,647 1398 INFO hago werkzeug: 101.78.142.90 - - [08/Jun/2023 08:37:02] "ESC[37mPOST /longpolling/poll HTTP/1.1ESC[0m" 200 - 1 0.000 0.003

=====

Thank you for your help!!!

Regards,
Simon