I’d create a third service that is periodically evaluating those two services. Evaluate with get_service the last_check_result and return state accordingly. Here you’ll find other example for using this function.
thanks for your hint. Unfortunately, I’m using the Icinga2 Web, which might be a poor solution, but I expect this “simple” Notification should do this job - but it doesn’t.
The notification apply rule creates notification objects based on the assign where clause.
The outcome then are one (or more) notification objects, one for each host or service.
There is no relationship between those notifications, so the logic you want is not possible.