Nano-SIM card is not recognized for the Sprint R850 Mobile Hotspot
This article troubleshoots issues related to the SIM card
Check whether the SIM card is properly installed. For details, see Insert or Remove a SIM Card.
Check the SIM card for damage.
Check the SIM card IC chip for scratches/corrosion.
Dirty SIM card (particularly IC chip) may prevent recognition. Clean gently with a soft cloth.
If none of these options work, please contact your service provider.