I need advice for those immediately done the upgrade of firmware. I have omada sdn controller v1 with version 4.2.8 in process of upgrading to the latest release 4.2.11 crash after the reboot process if an upgrade. Tried already to remove the poe supplied cable then reconnect. Seem it's crash during the reboot process. I have s backup USB always connected to this controller while I performed as well to have my system configuration and full 365 downloads back up of data from my controller before performing the upgrade. Its noticeable light for power is steady on notice can't see my static IP assigned to this controller from my router. Need to advise on how to restore first before resetting(pressing)  manually the pinhole reset button from the controller. I have a voucher system set up to maintain. 4 units out of 16 AP 225 outdoor can't link in mesh other EAP's. To mentioned online backup for my oc200 v1 backup controller is successful. Thank you.

Up to Date after several days hours of trial restoration remotely with my relatives (while I'm abroad) is a journey :)

Procedure Done in restoration from some advice read and share by @Fae 

1. Factory reset performed from recovery page of OC200 v1. The steps as follow.

a. Do the initial reset button procedure from a pinhole of oc200 while connected to the live network.

b. Disconnect the crash OC200 from the working network.

c. Take the laptop offline from the live network and in Network Card IPv4 set the static ip 192.168.0.10 / Subnet Mask 255.255.255.0 / Default Gateway 192.168.0.253 (which is the default fallback IP Address of OC200)

d. connect the lan cable (cat6) to eth2 of oc200 controller and lan of laptop.

e. Power on the OC200 (with iPad charger 2.1A also tried to use 1A iPhone charger in the process) while button steady press in pinhole reset for about 15 seconds and release.

f. From Laptop browser type 192.168.0.253 to come to access the recovery page of OC200 with 3 option menu, reboot, factory reset (default) and upgrade firmware.

g. I select factory reset and seen the controller rebooted with the blank page, not display. (Process again steps e and f for recovery page) I observe the oc200 doesn't factory reset since still shows the same recent firmware version with the latest build upgraded before it not totally lost in the network.

2. Downgrade / Upgrade Firmware from failed oc200 controller in the network.

a. From procedure 1 do the steps a up to f to come upon the recovery page.

b. First tried the downgrade by uploading the 4.2.8 Firmware and restart after the successful upgrade it reboots itself and pages no display.

c. Disconnect from local machine connection and connected it back to live network using the original PO Cable connected to my POE+ Switch TL-SG1008MP still not detected in-network and tried to manually add the device to account associating the device key which is 20 character key at the backside of your controller, display device is not available or offline.

d. I do as well the reset pinhole button while connected to network and still nothing happen I do check possibility of new mac device on live network but failed to see this. And performed once the default fallback address192.168.0.253  in browser while the oc200 is connected on poe switch live network still failed.

e. removed oc200 in live network and conenct it back to local pc setup with ethernet to lan port of machine Procedure 1 steps a-f).

f. I noticed the successful downgrade seem not happen while device performed the recovery sequence without the glitch or error message performing procedure 2 from a-  

b. it's kind weird after downgrade its reboot itself without any noticed of failure in the profcess while expectation device successfully downgraded.

g. Do the factory reset from recovery page and restart boot again to recovery page surprising nothing reset still got the latest frimware in oc200 v4.2.11 (which failed to work operate and seen in live network from my initial upgrade before i performed this long procedural process)

h. Knowing now the oc200 can't downgrade of factory reset from the stage of recovery. I do the same upgrade of firmware which already loaded from the crashed to operate unit after first original upgrade of controller (before this long escalation trials performed).

i. I downloaded the latest firmware v4.2.11 from tplink twice procedure performed from the unit to ensure i do have a corrupted firmware in process. to make it short both seems usually upgraded in process since normal steps followed without any error appear in the process.

j. Connected back the OC200 in live network and add device key in the process and to the last attempt still failed to see the device in the network while there's a power led light up and blinking network (seems normal activity blink) in poe lan port.

Out of several trials of reset, hardreset, soft reset (recovery page), and recovery upgrade/factory rest. NON of them works for me. I already contacted the technical support of vendor and agreed to send it back the device for the warranty claim and they will replicate I believe the same process performed in recovery or might they have a magic tricks out of my procedure and steps performed to fix or might a total replacement.