Note down the existing Wireless network name and passwords.
Find-out how many APs are there in the network.
If you have more than 1 AP, shut down the power for all the APs except the one AP (this will become the master AP when you turn down other APs). You can disable power by accessing the switch or remove the network cable.
Now you have just one AP plugged in the network and power. Push and hold the reset button for 12 seconds, AP will factory default and will come-up with setup wizard.
Complete the setup and this time make sure you enable password recovery.
Once master AP is up and running, remove it from the network and keep it a side.
Now power up the second AP and only perform factory reset.
Follow the same for rest of the APs but make sure you do not configure these APs.
Once all the APs are factory defaulted, remove them from the network and connect the master AP back to the network.
Check and make sure it is up and you can access it.
Now start connecting rest of the APs back to the network. All the other APs will auto join and get the config.