This appears to be a repeat of the post a few days ago: Cannot connect to port 8091 on localhost after installation
But I wanted to add some more info:
When I run netstat -a -b -p tcp when running the enterprise couchbase server, I get the expected output with *.* localhost:8091 LISTEN. But, When I run the community version, my netstat has no such line. I experienced this error on both the couchbase releases for Mac OSX (there is one experimental version for 10.11 and one for previous OSes).