Can't re-activate my CS6

[defaultcu6yupnb2q4l]

I've had CS6 installed on my Mac Pro and used if for years until the computer's power supply failed last week and it went dead. I bought a second, identical Mac Pro, and moved my hard drives into it and am back up and running again.

However, when I start up any CS6 application, up comes the CS6 Adobe Application Manager window asking me to sign in and re-enter the activation code (otherwise it says I'm running it on a trial basis for 30 days). That's no problem, I have the serial number right here, ready to enter. I click on the License This Software button which takes me to the Sign-In Required window.

When I click on Sign In Now, my e-mail address is already filled in for me, so I add the password in the box provided and click Sign In. All that happens is that it goes right back to the Sign-In Required window. 

Again I type in my password, click Sign In, and once again, back we go to the Sign In Now window. Around and around we go in circles, every time, stuck in a loop.

What am I doing wrong? Why won't the Adobe Application Manager move on to the window where I can put in the license key?

[John Waller]

I bought a second, identical Mac Pro, and moved my hard drives into it

Unrelated question: out of interest, which operating system are you now running? Not Catalina or Big Sur?

[defaultcu6yupnb2q4l]

John, it's OS 10.11.6  El Capitan.

From what I've read, El Capitan is the last OS that can run CS6 reliably. So I've stayed there.

A few years ago I switched computers like this, by just moving the hard drives over to a new box, and I had no trouble re-registering CS6 then, so I thought it would go as smoothly this time too. No such luck.

Tom