MongoDB all replica set members are "OTHER"?
When you enable authentication you must also specify (at the very least) a keyfile also (see step 1 in the procedure for enabling auth), setting auth=true without a keyfile will mean that the mongod processes will not be able to authenticate with each other (this is what the keyfile is used for).  Hence they cannot communicate, elect a primary, respond to heartbeats etc.

Follow the guide/docs linked above to create and configure a keyfile and your replica set should come up and elect a primary without an issue.