Unable to edit site with Sitejet: 500 error

Symptoms 

Trying to access Sitejet gives this error: 

CPANEL_ERROR: The API call failed with error code “500” and response “Can't connect to api.sitehub.io:443 ."

Cause

The server is unable to access the remote server api.sitehub.io over port 443. You can verify this with the following command:

# curl https://api.sitehub.io:443
curl: (35) OpenSSL SSL_connect: Connection reset by peer in connection to api.sitehub.io:443 

Resolution

Whitelist api.sitehub.io's IPs in your server and network firewall.

Note: The IPs returned may be different. You will need to run the command below to check the IPs.

# dig +short api.sitehub.io
api.sitejet.io.
136.243.5.208
88.198.22.168