Check if the PIN pad has power and is plugged in properly.
Check if the PIN pad is plugged into the POS correctly. If there are multiple integrated terminals on the premise, make sure the PIN pad is not swapped with another base/POS.
If the set-up is correct and the problem persists, check out this article to reboot the terminal.
If the problem persists after rebooting the terminal, check out the below articles which could be possible solutions to the issue or contact the Customer Support Team by submitting a ticket.