Is your management LAN a subnet other than the default of 192.168.0.0/24? Is your controller statically configured or does it use DHCP? Did you make a backup file for controller before the upgrade?

Ok, immediately take another backup of the new controller. Secondly take note of the new Admin password for devices, you will find this in the controller's site settings. With those 2 things done, it will be safe to try to reset things back into acstable mode.

  @d0ugmac1 

 

My first approach would be to factory reset the controller and let it get a DHCP ip from your 192.168.20.x subnet.

 

Login on this new IP, check your router's clients list to see what the ip is.  Then restore the controller from your backup file.  Change the Device Admin password if needed.   Restored controller should re adopt your devices  normally now.

  @d0ugmac1 

 

If that doesn't work, and you don't want to just rebuild your controller from scratch   then revert your OC300 to 5.7.6, restore your controller backup.  After the old controller is back up and running  back up just the site, not the whole controller.

 

Now upgrade the controller back to 5.9.x, set it up as new  then migrate your old site tobthe new controller.

Hello @Jeff_Parsons，

 

Thank you so much for taking the time to post the issue on TP-Link community!

 

To better assist you, I've created a support ticket via your registered email address, and escalated it to our support engineer to look into the issue. The ticket ID is TKID230539401, please check your email box and ensure the support email is well received. Thanks!

Once the issue is addressed or resolved, welcome to update this topic thread with your solution to help others who may encounter the same issue as you did.

 

Many thanks for your great cooperation and patience!

Hi @Jeff_Parsons,

 

Hope you are doing well. Our support team reported that they haven't received your email reply at all.

Have you ever received the support email whose case ID is TKID230539401? Or was your concern resolved on your own finally?

 

We are looking forward to hearing from you again.