Deployments from DeployHQ were working without a problem until a week ago, now when I try to deploy I get the following response on deployHQ:

‘Your server Production did not respond in a timely manner. Please ensure that it is up and there are no firewalls blocking access.’

I have restarted ssh.

I am able to ssh into the machine from the command line using my own ssh key.

I checked that the deployHQ IP ranges are whitelisted in the firewall:
SSH TCP 22 [deployHQs IP addresses]

the auth file for the user that DeployHQ uses to connect contains the correct public key.

deployHQ has the correct hostname, username and key set.

Nothing has changed on the server as far as I know.

What else can I look at, what should the 'ss’ command display if ssh is working correctly?