Found log entries in file /config/home-assistant.log:
2023-06-12 12:06:47.131 WARNING (MainThread) [homeassistant.components.climate] Setup of climate platform intesishome is taking over 10 seconds.
2023-06-12 12:07:26.922 WARNING (MainThread) [homeassistant.bootstrap] Waiting on integrations to complete setup: climate.intesishome
2023-06-12 12:08:26.988 WARNING (MainThread) [homeassistant.bootstrap] Waiting on integrations to complete setup: climate.intesishome
2023-06-12 12:08:49.308 ERROR (MainThread) [pyintesishome] Connection to 212.92.35.33:8210 failed with exception [Errno 110] Connect call failed ('212.92.35.33', 8210)
After opening the port 8210 for my home assistant vm in my firewall, it works.
Maybe it would be great to find the port information on the integration documentation page.