cann't deactivate old device online

I bought a new Mac last year. I forgot to deactivate on my old one. That leads to this notification when I tried to activate my Key on current device :
"This license has reached its activation limit and can no longer be used to activate new product copies"

please help me to DEACTIVATE on my old device so that I can activate on the current one, thank you.

 

I tried, but still cann't register, could you confirm this DEACTIVATION for me please?

 

please see the screenshot, it still does not work.