Why a PubSubEvent raised in a module is not being caught in the Shell?

Question

I have a problem that is an exact opposite of this: Prism, Event published in shell not caught in module!

The event is raised in one of my modules and is published like this:

_eventAggregator.GetEvent<ButtonEvent>().Publish("hello");

The subscription looks like this:

this._eventAggregator.GetEvent<ButtonEvent2>().Subscribe(method1, true);

When the event is raised, the other program modules' subscriptions work fine, but the shell does not recieve messages.

Any ideas how to fix this?