It is not uncommon for the drone and remote to disconnect after a firmware update.
The first step is to reboot both drone and controller.
If it remains unbound, with both powered on please connect the remote's USB-C port to the drone's USB-C port (on the battery compartment). Wait until the LED on the remote stops flashing green and ideally it will go into a steady blue, indicating the connection was restored. Then, you can unplug the cable.
If the Remote needs to be reset follow the additional instructions.