What version of AOS 8? It should all be supported and it should be working.
You should SSH directly into the controller and run the following command:
show mgmt-server message-counters process stm
If nothing is being sent the problem is on the controller side and you should check your AMON settings. If traffic is being sent, you might want to ensure that Airwave is configured for AMON data collection. If both of those are configured correctly, you might want to open a technical support case to see what could be wrong:
https://www.arubanetworks.com/support-services/contact-support/