Activate offline a Photoshop CS6 that was already activated in the past,request code not valid

Hello, I had a Photoshop CS6 License installed in a machine that for safety reasons cannot be connected to internet. The SW was activated using offline activation two years ago. That machine had to be resinstalled so the photoshop has been installed again. It request the activation again. So we have followed the instruccions given in https://exception.licenses.adobe.com/aoes/aoes/v1/t1?locale=en , obtaining the request code from the machine where the sw is installed.

But the request code is always refused as '"Request Code is invalid". Is it possible that the license is anyway blocked or something? When I type the serial number it appears as invalid too, but after pressing enter it appears ok. I have tried to remove the inner blanks of the code, press enter, and nothing seems to work. Do I have to de-activated the product first? How?

I have been talking online with customer care but the only solution given is to remotely connect to my machine to try the register. But the sw is not in my machine, it is in a machina that is not with me and cannot be connected.

Every help is welcome. Thanks in advance.