Thanks for reaching out malota,
It sounds like certain options are available to the owner of the group, but not to the guests. We can help.
Apple recently released an update to the Home app architecture. According to Upgrade to the new Home architecture, the following is true:
Any device that is connected to an upgraded home and not running the latest software will lose access to the home until the device is updated. This includes people that you invite to control your home.
At this time, Apple has temporarily paused updating to the new architecture, so there may be delays before this can be resolved:
We temporarily removed the option to upgrade to the new Home architecture. The option to upgrade will return soon. If you already upgraded, you are unaffected by this change.
Hope that helps.
Take care.