I'm trying to set up ddclient on my linux server to update dynu, but I keep getting timeouts. What's odd is that it actually looks like the update succeeds, but then the connection times out after that, causing ddclient to consider it a failure. (And not update its cache file properly.)

The following is the (verbose) output from a recent update:

INFO: setting IP address to [my_ip] for [my_hostname]
UPDATE: updating [my_hostname]
CONNECT: api.dynu.com
CONNECTED: using SSL
SENDING: GET /nic/update?system=dyndns&hostname=[my_hostname]&myip=[my_ip] HTTP/1.0
SENDING: Host: api.dynu.com
SENDING: Authorization: Basic [my_password_hash]
SENDING: User-Agent: ddclient/3.8.3
SENDING: Connection: close
SENDING:
RECEIVE: HTTP/1.1 200 OK
RECEIVE: Date: Mon, 07 May 2018 15:0:5 GMT
RECEIVE: Server: Dynu Web Server
RECEIVE: X-Powered-By: Dynu Dynamic DNS Service
RECEIVE: Content-Length: 5
RECEIVE: Content-Type: text/html
RECEIVE:
WARNING: TIMEOUT: api.dynu.com after 120 seconds
FAILED: updating [my_hostname]: Could not connect to api.dynu.com.

Any idea what the problem might be and/or how to fix?