When pairing both Zebra printer and tablet via Bluetooth it sometimes requires a PIN. If your PIN is incorrect you can reset this by downloading Zebra Setup Utilities. See the following link to download this.
https://www.zebra.com/us/en/products-services/software/zebralink/zebra-setup-utility.html
INSTRUCTIONS: How to Reset Bluetooth pin on Zebra RW420 Printer
1. Connect the Mini USB cable to the Printer, the other end to the computer.
2. Download and Install Zebra Setup Utilities.
3. Open Zebra Setup Utilities after you have installed it.
4. Here click on Install new Printer if it didn’t auto detected your printer.
5. Click Next to the Wizard, Install Printer, and look for your printer model in the printers: Box.
6. Click on next, select USB, and click finish to install the printer.
7. Once installed, in the Zebra Setup Utilities window select the printer.
8. Click on Configure Printer Connectivity to open the Conectivity Setup Wizard.
9. Here select Bluetooth and click on next.
10. Then turn on Authentication, to be able to add an authentication pin of your choice.
11. Once done click on next and finish to reset the Bluetooth pin.
12. Disconnect it from the computer and your device is enabled for Bluetooth connectivity.