Dear David,
In that case, the only option you have is to perform a Hardware Reset.
But this is an extremely sensitive operation and you need to be cautious while doing it.
Here’s the step to follow.

Through Hardware Settings
This feature allows the administrator to reset the terminal to factory default settings through hardware settings i.e. by connecting a combination of GPIO and Wiegand external pins as described below:
Steps to perform Factory Reset through Hardware settings
Step 1 : Power off the terminal
Step 2 : The terminal is detached from the wall
Step 3 : Access the external pins of the terminal and connects the following pins:
 GPO_0 to the WIEGAND_IN0
 GPI_1 to the WIEGAND_OUT1
Step 4 : Power-on the terminal
Step 5 : After the terminal power on, the terminal is reset to the factory settings
List of setting to be reset
1. Clear all databases
2. Remove all custom files
3. Clear KMS
4. Set all the configuration parameters to default value
Note
The reset will occur only when the hardward pins are connected and the tamper is triggered for the terminal (i.e. terminal is detached from the wall).