The TEST notification in aCalendar notification settings should detect this and guide you to power saving settings, which need to be changed.
This is a Huawei firmware bug introduced with EMUI 8, that is blocking the broadcast of due event notifications, against the Android specification (ACTION_EVENT_REMINDER should be whitelisted).
As aCalendar receives no broadcast, it needs to run as a service to fix this Huawei bug.
As background services are no longer allowed with Android 8, we provide a foreground service which also provides the current date in the status bar.
You can enable this as Sticky Date in notification settings. This should also fix the bug with Huawei devices delaying all-day notifications by 9h to fix a bug in the Huawei calendar app.
We have a limited selection of Huawei devices and would be happy if you can provide feedback if this works - please use the THUMBS UP icon on this page to let us know if it works, use the THUMBS DOWN icon (and include details on device, Android version, EMUI version and widget used) if it doesn't.