1. Whenever I start the unit the WIFI has to be turned on again. How do I keep the units WIFI on?

A.  Swipe the screen down to reveal the Wifi icon, Press and hold it to open the WIFI options and do the follow the below steps.

Enter Wifi preferences

Turn on WIFI Automatically

B.  In players support wireless Carplay and Android Auto, it will occupy the WIFI channel. So you  also need to close the auto connection for Carplay and Android auto.
For Zlink following: Zlink-Settings-Background Connection-OFF
For Carletter following: Carletter-Settings-Connect Automatically-OFF 

2. How to Fault Find SIM Cards

1). This system uses Micro SIM Cards

2) After inserting the SIM card, the device MUST be restarted in order to read the Sim card. Swipe the screen task bar down and select "Reboot". Please make sure you have connected the 4G antenna.

3) If SIM card has PIN code, the SIM card will NOT work. Please remove PIN code from sim card before trying to make SIM card work. Sometimes your network operator will have to be contacted to remove PIN

4) If all steps above fail, check with a different SIM card you know works and has no PIN code and repeat steps 1 & 2.

7) Don't use Sprint and Verizon sim cards. T-Mobile pre-paid works and AT&T is ok

4G LTE band support

How to add an APN?

Car Settings-System-More-Network & internet-Mobile network-Advanced-Access Point Names- “+”
Usually you only need to fill the Name, APN, MNC, MCC, then it will work correctly.

6) Some SIM cards are thinner than regular SIM cards - If you insert your sim card and it is not registering as being inserted on the head unit, you may have to place tape on the backside of the SIM card so it can make better contact.

5) Verify your APN settings are correct according to your provider (must be tablet APN settings)