How to debug UCP not running?

Running FreePBX 13.0.49. UCP Node Server 13.0.17. In Dashboard, UCP Daemon is not running.

If I do a fwconsole stop ucpnode the console tells me the server is stopping and then stopped. A fwconsole start ucpnode tells me the server is starting and then started.

Looking at the ucp log (cat /var/log/asterisk/ucp_out.log) I have a single line consisting of…

Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…Starting FreePBX…

Can anyone suggest where I ought to start looking to discover why it never actually runs?

Many thanks.