Try running these commands through command line:
fmsadmin restart wpe
fmsadmin restart adminserver
Then try again.
Thanks for that, but I'm afraid it didn't help. I have just noticed that there are others that have seen a similar problem…
Since only 14v4 is supported on El Capitan: did you start with a full installer? If not it could be some artifact of a non-supported version that is still there?
I would completely uninstall what you have, delete the remnant folders and files (crucial!), reboot the machine and then try to install with the full v4 installer.
Perfect. Thanks. Removed the 'upgrade version', downloaded full installer and deployed that. It's now working again.