If you issue 'show ethernet-switching global-information', what is listed for 'Global Mode'?
Which version of software are you using? It appears that command is available starting in 15.1X49-D40, and transparent-bridge is the default mode until 15.1X49-D100. (https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/protocols-edit-global-mode.html)