Im using Nearby and Eddystone URL to broadcast notifications to Chrome on mobile. After provisioning and setting up of the beacons, it works great. The notifications shows up in the notification drawer. However, if it was dismissed by accident or intentionally, it doesn't show up anymore. I read somewhere that it goes "silent" for some time to avoid pestering the users. But in my case, it never returned unless I provision the beacons again.
Two questions:
If the notification has been dismissed on a device recently, that device may not show another notification a period of time. You can reset the backoff policy by opening Settings … Google … Nearby. Read this and more troubleshooting Tips.
There's nothing you can do about this as it's controlled by Google/Android.