installation/contact support

if you have an old os, your default browser must support tls 1.2, https://helpx.adobe.com/x-productkb/multi/eol-tls-support.html

to test your default browser's tls you can use , https://clienttest.ssllabs.com:8443/ssltest/viewMyClient.html

otherwise, confirm that you can connect to the secure adobe servers by reading, http://helpx.adobe.com/x-productkb/policy-pricing/activation-network-issues.html

do you see both logos after clicking "link"?

if you can and still see a connection error try these steps, https://helpx.adobe.com/download-install/kb/unable-to-reach-adobe-servers.html

if those fail, make sure you also tried the steps at, https://helpx.adobe.com/download-install/kb/common-network-connectivity-issues.html

if those all fail, contact adobe support using chat so they can inspect your computer. there are 3 ways to contact adobe; chat, phone and twitter:

chat:
use a browser that allows popups and cookies
and click here, https://helpx.adobe.com/contact.html?rghtup=autoOpen
in the chat field (lower right), type AGENT
be patient, it can take quite a while to reach a human.

phone:
https://helpx.adobe.com/contact/phone.html

twitter:
tweet @AdobeCare

p.s. if you're contacted by anyone (via email or private message), it's much more likely to be a scammer than an adobe representative. ie, double check for an employee badge if contacted in the forums and look for an adobe.com domain in the email address if you click reply to an email. then check again and be very suspicious. any other method of contacting (or offering to contact you) is almost certainly a scam, https://community.adobe.com/t5/using-the-community-discussions/staying-safe-in-the-adobe-support-community/td-p/12919684/redirect_from_archived_page/true