keep the leading / so /privkey.pem etc
had to uninstall and reinstall duckdns addon.
the /ssl/ folder was empty so it had to recreate the files. that was the error.
back to square 1 that the url didnt work.
for the record:
my network consists of a cablemodem with routing capabilities and a router. I thought i had disabled the routing capabilities, but that was not so.