Connection time out from gitlab

I have registered 2 runners for my project, they worked just fine since yesterday. but suddenly they stop to work. when I start pipelines, I see runner output which saying

ERROR: Registering runner... failed                 runner=^^^^^^^^ status=couldn't execute POST against https://gitlab.com/api/v4/runners: Post https://gitlab.com/api/v4/runners: dial tcp 35.231.145.151:443: i/o timeout
PANIC: Failed to register this runner. Perhaps you are having network problems 

also when I run curl https://gitlab.com/ again its print Connection time out after a while. my server is in Canada.
these days I did nothing with the server and I wonder how this network problem happen to the server. I’ll appreciate anybody which help me to debug this issue or give me insight for starting to troubleshoot.

This is an old post, but this issue happened to me this morning.

fixed by restarting the docker service:

FYI - currently working on CentOS7

sudo systemctl restart docker