You have added a SIM card in the slot, you know you have it the right way up and you have have tried a different SIM card just to be sure.
You keep getting the message that SIM slot: SIM empty.
Some models for the branded android headunits have the facility to add a SIM card for Data. This means you don’t need to hot spot your phone for an internet connection but it does mean you need a second SIM plan to get the additional SIM card.
No Hot Spot
Not having to hot spot your phone, or not even having to bring your phone with you can be a great advantage. Maybe it is a locked down works phone that you use or you don’t want to set up hot spotting each time. Having the facility for a dedicated SIM card in your android headunit can be a huge plus.
But what happens if the SIM card is not recognised by the android headunit. There is a warning message that SIM Slot: SIM empty, No SIM detected or something similar that indicates the SIM card is not working in the head unit.
You’ve already tried a different SIM card.
You know it works because you tried the new SIM card in a phone.
Try inserting the SIM card in the slot and power down the head unit. Switch it off and disconnect the car battery. When you reconnect the car battery it will force a cold boot of the android headunit. It may take longer to cold boot. During this cold boot (long bootup) the android headunit checks for the SIM card presence and initialises it. When the unit has fully rebooted from cold, look now for the SIM card SIM slot presence.
You should now have a SIM card active in the SIM slot and data is active