I have installed the latest version of HAOS for R Pi 5, tried to install add-on Advanced SSH & Web Terminal which is appearing in the left menu but when it is selected I get message "The add-on is not running. Do you want to start it now? Click on START ADD-ON. Next display has message in top left of screen 5502: Bad Gateway. Message below "The add-on seems to be not ready, it might still be starting. Do you want to try again? Select RETRY multiple times, nothing happens. When installing I enable start on boot. I have rebooted the system, logged off and back on, still not working. Help anyone?
#Advanced SSH & Web Terminal not starting
nova hinge
hallow gale
Did you configure the username and password/SSH key on the add-on's settings page? And saved those changes?
nova hinge
I configured the username and password on the settings page, don't know about SSH key.
Just checked configuration again, appears I didn't save 
What goes into authorized_keys?
hallow gale
The public SSH key, if used