There are a few things to check if your Hotspot has already been registered and is online but you're unable to connect to it on your device.
1. Make sure that the device you are attempting to connect to the Hotspot with is currently running the latest version of the Helium Mobile application and is currently logged into an active Helium Mobile Subscription account.
2. Make sure that the device you are attempting to connect from has its Dynamic Coverage Enhanced enabled.
3. Verify whether or not you have hit the 5GB reward cap for the month on this particular line. By default Helium Mobile Hotspots do not allow Unrewarded Traffic to be passed through the Hotspot. This means that any line that has hit their 5GB limit for the month, will no longer be able to connect to this Hotspot.
You can manually enable your Helium Mobile Hotspot to allow unrewarded traffic to pass through it by simply heading to your Helium Mobile Dashboard and logging in.
From there, simply find the Helium Mobile Hotspot you are attempting to connect to, and make sure that the Allow Unrewarded Traffic toggle has been enabled:
Once you have this toggled on, you should now be able to connect to your hotspot, even if you have reached your reward cap for the month.