Failing to use Add-on with SIP Card in Home Assistant

[kapkinn]

I did successfully (?) install the add-on (no errors in the log file) and the integration also seems to work (Persons have been created as extensions).
I did create a SIP Card, which is displayed fine. But calling or receiving a call doesn't work.
Assuming I have an issue with the certificate. Currently I do use "Generate SSL Certifcate" and can only run http, no https.
Also if I try to connect via a VoIP Client, the client app does try, but fails and the log does show several error lines related to SSL.

The target configuration shall be used to connect a SIP Video doorbell (Hikvision) and route the call to internal (same LAN/WLAN) devices (iPad, iPhone). No external calls needed.

Would be happy to receive some help.
Manfred

Appendix: Card setup

type: custom:sipjs-card
server: localhost
port: '8089'
button_size: '48'
state_color: true
auto_answer: false
hide_me: false
custom_title: Test
video: true
dtmfs: []
extensions:

• person: person.mm
  name: mm
  extension: '101'
  secret: xxxxxx
  icon: mdi:person
  camera: ''
• person: person.bb
  name: bb
  extension: '102'
  secret: xxxxxx
  icon: mdi:person
  camera: ''
  iceTimeout: 5
  prefix: ''
  ringtone: /local/asterisk/ringtone.mp3
  ringbacktone: /local/asterisk/ringtone.mp3
  backup_name: Tablet
  backup_extension: '100'
  backup_secret: xxxxxx