Deactivated studio 2015 to move it to another computer. Now activation code wont work in none of the computers "0 license available". Retried deactivation offline and an error occurs every time. Internet connection working fine

I have deactivated my trados studio 2015 (single user license) to move it to another computer. Now every time I enter my activation code, I get the message "0 license available". My account still shows there's 1 license in use. I have retried deactivation offline to get a deactivation certificate but I can't get connected to server: an error occurs every time and I'm asked to look for support. I have also refreshed the connection proxy and tested internet connection - that's working fine. What should I do? txs