Licensing works in service, not in activity: ERROR_COMMUNICATING_WITH_APPCENTER_0113

In my app, I check for the license in my service, not in an activity. I managed to make it (mostly) work fine, the problem is that, when the user gets an ERROR_NOT_AUTHENTICATED error, the library is unable to show the alert dialog to prompt for the Android PIT credentials, since you cannot launch dialogs from a service. So, I tried to add a way to ALSO check for the license in the main activity of my app: the idea is to redirect my user to my app when the license check fails, so that the alert dialog can be displayed there.

Unfortunately, this doesn't work: the license check works as expected in the service, but if I try to do the same (with exactly the same code) in my activity, I always get a ERROR_COMMUNICATING_WITH_APPCENTER_0113 error. The documentation is very poor to be polite, and this error is notr even documented anywhere. I had to go through the code to see this happens when a Null Pointer Exception is met somewhere in the request: obviously where is still a mystery, since from that point on we enter the dark realm of remote calls.

What's going wrong and why? how do I fix it? and if I cannot fix it, how can I provide those credentials in a different way?

9 months and still NO answer?? and this is what you call support?
I made a serious mistake registering my app on Android PIT, from where no I cannot even go away from, considering this would affect the users who bought the app so far.