Does RMS show that the device is offline in RMS? Assuming monitoring is enabled in RMS and on the device, then your device should be online. Of course, if it has internet connectivity and you have credits available.
Could you try to unregister the device from RMS and add it back again?
When it comes to RMS data, the 'remaining company data' is used for all devices within the company. The data next to each device is what is available for that specific device. This basically refers to data packs. Hence, if you have company data available and the device is within your company, the device should be able to use company data even if the data field shows no remaining data for that specific device. I hope this clears things up.